security/ccsecurity/policy_io.c

/*
 * security/ccsecurity/policy_io.c
 *
 * Copyright (C) 2005-2009  NTT DATA CORPORATION
 *
 * Version: 1.7.0-pre   2009/08/08
 *
 * This file is applicable to both 2.4.30 and 2.6.11 and later.
 * See README.ccs for ChangeLog.
 *
 */

#include "internal.h"

/* Lock for protecting ccs_profile->comment  */
static DEFINE_SPINLOCK(ccs_profile_comment_lock);

static bool ccs_profile_entry_used[CCS_MAX_CONTROL_INDEX +
                                   CCS_MAX_CAPABILITY_INDEX + 1];

/* String table for functionality that takes 4 modes. */
static const char *ccs_mode_4[4] = {
        "disabled", "learning", "permissive", "enforcing"
};
/* String table for functionality that takes 2 modes. */
static const char *ccs_mode_2[4] = {
        "disabled", "enabled", "enabled", "enabled"
};

/* Table for profile. */
static struct {
        const char *keyword;
        unsigned int current_value;
        const unsigned int max_value;
} ccs_control_array[CCS_MAX_CONTROL_INDEX] = {
        [CCS_MAC_FOR_FILE]        = { "MAC_FOR_FILE",        0, 3 },
        [CCS_MAC_FOR_IOCTL]       = { "MAC_FOR_IOCTL",       0, 3 },
        [CCS_MAC_FOR_FILEATTR]    = { "MAC_FOR_FILEATTR",    0, 3 },
        [CCS_MAC_FOR_ARGV0]       = { "MAC_FOR_ARGV0",       0, 3 },
        [CCS_MAC_FOR_ENV]         = { "MAC_FOR_ENV",         0, 3 },
        [CCS_MAC_FOR_NETWORK]     = { "MAC_FOR_NETWORK",     0, 3 },
        [CCS_MAC_FOR_SIGNAL]      = { "MAC_FOR_SIGNAL",      0, 3 },
        [CCS_MAC_FOR_NAMESPACE]   = { "MAC_FOR_NAMESPACE",   0, 3 },
        [CCS_RESTRICT_AUTOBIND]   = { "RESTRICT_AUTOBIND",   0, 1 },
        [CCS_MAX_ACCEPT_ENTRY]
        = { "MAX_ACCEPT_ENTRY", CONFIG_CCSECURITY_MAX_ACCEPT_ENTRY, INT_MAX },
#ifdef CONFIG_CCSECURITY_AUDIT
        [CCS_MAX_GRANT_LOG]
        = { "MAX_GRANT_LOG", CONFIG_CCSECURITY_MAX_GRANT_LOG, INT_MAX },
        [CCS_MAX_REJECT_LOG]
        = { "MAX_REJECT_LOG", CONFIG_CCSECURITY_MAX_REJECT_LOG, INT_MAX },
#endif
        [CCS_VERBOSE]             = { "TOMOYO_VERBOSE",      1, 1 },
        [CCS_SLEEP_PERIOD]
        = { "SLEEP_PERIOD",        0, 3000 }, /* in 0.1 second */
};

/* Permit policy management by non-root user? */
static bool ccs_manage_by_non_root;

/**
 * ccs_quiet_setup - Set CCS_VERBOSE=0 by default.
 *
 * @str: Unused.
 *
 * Returns 0.
 */
static int __init ccs_quiet_setup(char *str)
{
        ccs_control_array[CCS_VERBOSE].current_value = 0;
        return 0;
}

__setup("CCS_QUIET", ccs_quiet_setup);

/**
 * ccs_io_printf - Transactional printf() to "struct ccs_io_buffer" structure.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @fmt:  The printf()'s format string, followed by parameters.
 *
 * Returns true on success, false otherwise.
 *
 * The snprintf() will truncate, but ccs_io_printf() won't.
 */
bool ccs_io_printf(struct ccs_io_buffer *head, const char *fmt, ...)
{
        va_list args;
        int len;
        int pos = head->read_avail;
        int size = head->readbuf_size - pos;
        if (size <= 0)
                return false;
        va_start(args, fmt);
        len = vsnprintf(head->read_buf + pos, size, fmt, args);
        va_end(args);
        if (pos + len >= head->readbuf_size)
                return false;
        head->read_avail += len;
        return true;
}

/**
 * ccs_find_or_assign_new_profile - Create a new profile.
 *
 * @profile: Profile number to create.
 *
 * Returns pointer to "struct ccs_profile" on success, NULL otherwise.
 */
struct ccs_profile *ccs_find_or_assign_new_profile(const unsigned int
                                                   profile)
{
        struct ccs_profile *ptr;
        struct ccs_profile *entry;
        int i;
        if (profile >= MAX_PROFILES)
                return NULL;
        ptr = ccs_profile_ptr[profile];
        if (ptr)
                return ptr;
        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        mutex_lock(&ccs_policy_lock);
        ptr = ccs_profile_ptr[profile];
        if (!ptr && ccs_memory_ok(entry, sizeof(*entry))) {
                ptr = entry;
                for (i = 0; i < CCS_MAX_CONTROL_INDEX; i++)
                        ptr->value[i] = ccs_control_array[i].current_value;
                /*
                 * Needn't to initialize "ptr->capability_value"
                 * because they are always 0.
                 */
                mb(); /* Avoid out-of-order execution. */
                ccs_profile_ptr[profile] = ptr;
                entry = NULL;
        }
        mutex_unlock(&ccs_policy_lock);
        kfree(entry);
        return ptr;
}

/**
 * ccs_write_profile - Write profile table.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_write_profile(struct ccs_io_buffer *head)
{
        char *data = head->write_buf;
        unsigned int i;
        unsigned int value;
        char *cp;
        struct ccs_profile *ccs_profile;
        i = simple_strtoul(data, &cp, 10);
        if (data != cp) {
                if (*cp != '-')
                        return -EINVAL;
                data = cp + 1;
        }
        ccs_profile = ccs_find_or_assign_new_profile(i);
        if (!ccs_profile)
                return -EINVAL;
        cp = strchr(data, '=');
        if (!cp)
                return -EINVAL;
        *cp = '\0';
        if (!strcmp(data, "COMMENT")) {
                const struct ccs_path_info *new_comment
                        = ccs_get_name(cp + 1);
                const struct ccs_path_info *old_comment;
                /* Protect reader from ccs_put_name(). */
                /***** CRITICAL SECTION START *****/
                spin_lock(&ccs_profile_comment_lock);
                old_comment = ccs_profile->comment;
                ccs_profile->comment = new_comment;
                spin_unlock(&ccs_profile_comment_lock);
                /***** CRITICAL SECTION END *****/
                ccs_put_name(old_comment);
                ccs_profile_entry_used[0] = true;
                return 0;
        }
        if (ccs_str_starts(&data, KEYWORD_MAC_FOR_CAPABILITY)) {
                if (sscanf(cp + 1, "%u", &value) != 1) {
                        for (i = 0; i < 4; i++) {
                                if (strcmp(cp + 1, ccs_mode_4[i]))
                                        continue;
                                value = i;
                                break;
                        }
                        if (i == 4)
                                return -EINVAL;
                }
                if (value > 3)
                        value = 3;
                for (i = 0; i < CCS_MAX_CAPABILITY_INDEX; i++) {
                        if (strcmp(data, ccs_capability_control_keyword[i]))
                                continue;
                        ccs_profile->capability_value[i] = value;
                        ccs_profile_entry_used[i + 1 + CCS_MAX_CONTROL_INDEX]
                                = true;
                        return 0;
                }
                return -EINVAL;
        }
        for (i = 0; i < CCS_MAX_CONTROL_INDEX; i++) {
                if (strcmp(data, ccs_control_array[i].keyword))
                        continue;
                if (sscanf(cp + 1, "%u", &value) != 1) {
                        int j;
                        const char **modes;
                        switch (i) {
                        case CCS_RESTRICT_AUTOBIND:
                        case CCS_VERBOSE:
                                modes = ccs_mode_2;
                                break;
                        default:
                                modes = ccs_mode_4;
                                break;
                        }
                        for (j = 0; j < 4; j++) {
                                if (strcmp(cp + 1, modes[j]))
                                        continue;
                                value = j;
                                break;
                        }
                        if (j == 4)
                                return -EINVAL;
                } else if (value > ccs_control_array[i].max_value) {
                        value = ccs_control_array[i].max_value;
                }
                ccs_profile->value[i] = value;
                ccs_profile_entry_used[i + 1] = true;
                return 0;
        }
        return -EINVAL;
}

/**
 * ccs_read_profile - Read profile table.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0.
 */
static int ccs_read_profile(struct ccs_io_buffer *head)
{
        static const int ccs_total
                = CCS_MAX_CONTROL_INDEX + CCS_MAX_CAPABILITY_INDEX + 1;
        int step;
        if (head->read_eof)
                return 0;
        for (step = head->read_step; step < MAX_PROFILES * ccs_total; step++) {
                const u8 index = step / ccs_total;
                u8 type = step % ccs_total;
                const struct ccs_profile *ccs_profile = ccs_profile_ptr[index];
                head->read_step = step;
                if (!ccs_profile)
                        continue;
                if (!ccs_profile_entry_used[type])
                        continue;
                if (!type) { /* Print profile' comment tag. */
                        bool done;
                        /***** CRITICAL SECTION START *****/
                        spin_lock(&ccs_profile_comment_lock);
                        done = ccs_io_printf(head, "%u-COMMENT=%s\n",
                                             index, ccs_profile->comment ?
                                             ccs_profile->comment->name : "");
                        spin_unlock(&ccs_profile_comment_lock);
                        /***** CRITICAL SECTION END *****/
                        if (!done)
                                break;
                        continue;
                }
                type--;
                if (type >= CCS_MAX_CONTROL_INDEX) {
                        const int i = type - CCS_MAX_CONTROL_INDEX;
                        const u8 value = ccs_profile->capability_value[i];
                        if (!ccs_io_printf(head,
                                           "%u-" KEYWORD_MAC_FOR_CAPABILITY
                                           "%s=%s\n", index,
                                           ccs_capability_control_keyword[i],
                                           ccs_mode_4[value]))
                                break;
                } else {
                        const unsigned int value = ccs_profile->value[type];
                        const char **modes = NULL;
                        const char *keyword = ccs_control_array[type].keyword;
                        switch (ccs_control_array[type].max_value) {
                        case 3:
                                modes = ccs_mode_4;
                                break;
                        case 1:
                                modes = ccs_mode_2;
                                break;
                        }
                        if (modes) {
                                if (!ccs_io_printf(head, "%u-%s=%s\n", index,
                                                   keyword, modes[value]))
                                        break;
                        } else {
                                if (!ccs_io_printf(head, "%u-%s=%u\n", index,
                                                   keyword, value))
                                        break;
                        }
                }
        }
        if (step == MAX_PROFILES * ccs_total)
                head->read_eof = true;
        return 0;
}

/* The list for "struct ccs_policy_manager_entry". */
LIST_HEAD(ccs_policy_manager_list);

/**
 * ccs_update_manager_entry - Add a manager entry.
 *
 * @manager:   The path to manager or the domainnamme.
 * @is_delete: True if it is a delete request.
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_update_manager_entry(const char *manager, const bool is_delete)
{
        struct ccs_policy_manager_entry *entry = NULL;
        struct ccs_policy_manager_entry *ptr;
        const struct ccs_path_info *saved_manager;
        int error = is_delete ? -ENOENT : -ENOMEM;
        bool is_domain = false;
        if (ccs_is_domain_def(manager)) {
                if (!ccs_is_correct_domain(manager))
                        return -EINVAL;
                is_domain = true;
        } else {
                if (!ccs_is_correct_path(manager, 1, -1, -1))
                        return -EINVAL;
        }
        saved_manager = ccs_get_name(manager);
        if (!saved_manager)
                return -ENOMEM;
        if (!is_delete)
                entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        mutex_lock(&ccs_policy_lock);
        list_for_each_entry_rcu(ptr, &ccs_policy_manager_list, list) {
                if (ptr->manager != saved_manager)
                        continue;
                ptr->is_deleted = is_delete;
                error = 0;
                break;
        }
        if (!is_delete && error && ccs_memory_ok(entry, sizeof(*entry))) {
                entry->manager = saved_manager;
                saved_manager = NULL;
                entry->is_domain = is_domain;
                list_add_tail_rcu(&entry->list, &ccs_policy_manager_list);
                entry = NULL;
                error = 0;
        }
        mutex_unlock(&ccs_policy_lock);
        ccs_put_name(saved_manager);
        kfree(entry);
        return error;
}

/**
 * ccs_write_manager_policy - Write manager policy.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_write_manager_policy(struct ccs_io_buffer *head)
{
        char *data = head->write_buf;
        bool is_delete = ccs_str_starts(&data, KEYWORD_DELETE);
        if (!strcmp(data, "manage_by_non_root")) {
                ccs_manage_by_non_root = !is_delete;
                return 0;
        }
        return ccs_update_manager_entry(data, is_delete);
}

/**
 * ccs_read_manager_policy - Read manager policy.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0.
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_read_manager_policy(struct ccs_io_buffer *head)
{
        struct list_head *pos;
        ccs_check_read_lock();
        if (head->read_eof)
                return 0;
        list_for_each_cookie(pos, head->read_var2, &ccs_policy_manager_list) {
                struct ccs_policy_manager_entry *ptr;
                ptr = list_entry(pos, struct ccs_policy_manager_entry, list);
                if (ptr->is_deleted)
                        continue;
                if (!ccs_io_printf(head, "%s\n", ptr->manager->name))
                        return 0;
        }
        head->read_eof = true;
        return 0;
}

/**
 * ccs_is_policy_manager - Check whether the current process is a policy manager.
 *
 * Returns true if the current process is permitted to modify policy
 * via /proc/ccs/ interface.
 *
 * Caller holds ccs_read_lock().
 */
static bool ccs_is_policy_manager(void)
{
        struct ccs_policy_manager_entry *ptr;
        const char *exe;
        struct task_struct *task = current;
        const struct ccs_path_info *domainname
                = ccs_current_domain()->domainname;
        bool found = false;
        ccs_check_read_lock();
        if (!ccs_policy_loaded)
                return true;
        if (task->ccs_flags & CCS_TASK_IS_POLICY_MANAGER)
                return true;
        if (!ccs_manage_by_non_root && (current_uid() || current_euid()))
                return false;
        list_for_each_entry_rcu(ptr, &ccs_policy_manager_list, list) {
                if (!ptr->is_deleted && ptr->is_domain
                    && !ccs_pathcmp(domainname, ptr->manager)) {
                        /* Set manager flag. */
                        task->ccs_flags |= CCS_TASK_IS_POLICY_MANAGER;
                        return true;
                }
        }
        exe = ccs_get_exe();
        if (!exe)
                return false;
        list_for_each_entry_rcu(ptr, &ccs_policy_manager_list, list) {
                if (!ptr->is_deleted && !ptr->is_domain
                    && !strcmp(exe, ptr->manager->name)) {
                        found = true;
                        /* Set manager flag. */
                        task->ccs_flags |= CCS_TASK_IS_POLICY_MANAGER;
                        break;
                }
        }
        if (!found) { /* Reduce error messages. */
                static pid_t ccs_last_pid;
                const pid_t pid = current->pid;
                if (ccs_last_pid != pid) {
                        printk(KERN_WARNING "%s ( %s ) is not permitted to "
                               "update policies.\n", domainname->name, exe);
                        ccs_last_pid = pid;
                }
        }
        kfree(exe);
        return found;
}

/**
 * ccs_find_condition_part - Find condition part from the statement.
 *
 * @data: String to parse.
 *
 * Returns pointer to the condition part if it was found in the statement,
 * NULL otherwise.
 */
static char *ccs_find_condition_part(char *data)
{
        char *cp = strstr(data, " if ");
        if (cp) {
                while (1) {
                        char *cp2 = strstr(cp + 3, " if ");
                        if (!cp2)
                                break;
                        cp = cp2;
                }
                *cp++ = '\0';
        } else {
                cp = strstr(data, " ; set ");
                if (cp)
                        *cp++ = '\0';
        }
        return cp;
}

/**
 * ccs_is_select_one - Parse select command.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @data: String to parse.
 *
 * Returns true on success, false otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static bool ccs_is_select_one(struct ccs_io_buffer *head, const char *data)
{
        unsigned int pid;
        struct ccs_domain_info *domain = NULL;
        ccs_check_read_lock();
        if (!strcmp(data, "allow_execute")) {
                head->read_execute_only = true;
                return true;
        }
        if (sscanf(data, "pid=%u", &pid) == 1) {
                struct task_struct *p;
                /***** CRITICAL SECTION START *****/
                read_lock(&tasklist_lock);
                p = find_task_by_pid(pid);
                if (p)
                        domain = ccs_task_domain(p);
                read_unlock(&tasklist_lock);
                /***** CRITICAL SECTION END *****/
        } else if (!strncmp(data, "domain=", 7)) {
                if (ccs_is_domain_def(data + 7))
                        domain = ccs_find_domain(data + 7);
        } else
                return false;
        head->write_var1 = domain;
        /* Accessing read_buf is safe because head->io_sem is held. */
        if (!head->read_buf)
                return true; /* Do nothing if open(O_WRONLY). */
        head->read_avail = 0;
        ccs_io_printf(head, "# select %s\n", data);
        head->read_single_domain = true;
        head->read_eof = !domain;
        if (domain) {
                struct ccs_domain_info *d;
                head->read_var1 = NULL;
                list_for_each_entry_rcu(d, &ccs_domain_list, list) {
                        if (d == domain)
                                break;
                        head->read_var1 = &d->list;
                }
                head->read_var2 = NULL;
                head->read_bit = 0;
                head->read_step = 0;
                if (domain->is_deleted)
                        ccs_io_printf(head, "# This is a deleted domain.\n");
        }
        return true;
}

/**
 * ccs_write_domain_policy - Write domain policy.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_write_domain_policy(struct ccs_io_buffer *head)
{
        char *data = head->write_buf;
        struct ccs_domain_info *domain = head->write_var1;
        bool is_delete = false;
        bool is_select = false;
        unsigned int profile;
        struct ccs_condition *cond = NULL;
        char *cp;
        int error;
        if (ccs_str_starts(&data, KEYWORD_DELETE))
                is_delete = true;
        else if (ccs_str_starts(&data, KEYWORD_SELECT))
                is_select = true;
        if (is_select && ccs_is_select_one(head, data))
                return 0;
        /* Don't allow updating policies by non manager programs. */
        if (!ccs_is_policy_manager())
                return -EPERM;
        if (ccs_is_domain_def(data)) {
                domain = NULL;
                if (is_delete)
                        ccs_delete_domain(data);
                else if (is_select)
                        domain = ccs_find_domain(data);
                else
                        domain = ccs_find_or_assign_new_domain(data, 0);
                head->write_var1 = domain;
                return 0;
        }
        if (!domain)
                return -EINVAL;

        if (sscanf(data, KEYWORD_USE_PROFILE "%u", &profile) == 1
            && profile < MAX_PROFILES) {
                if (ccs_profile_ptr[profile] || !ccs_policy_loaded)
                        domain->profile = (u8) profile;
                return 0;
        }
        if (!strcmp(data, KEYWORD_IGNORE_GLOBAL_ALLOW_READ)) {
                domain->ignore_global_allow_read = !is_delete;
                return 0;
        }
        if (!strcmp(data, KEYWORD_IGNORE_GLOBAL_ALLOW_ENV)) {
                domain->ignore_global_allow_env = !is_delete;
                return 0;
        }
        cp = ccs_find_condition_part(data);
        if (cp) {
                cond = ccs_get_condition(cp);
                if (!cond)
                        return -EINVAL;
        }
        if (ccs_str_starts(&data, KEYWORD_ALLOW_CAPABILITY))
                error = ccs_write_capability_policy(data, domain, cond,
                                                    is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_NETWORK))
                error = ccs_write_network_policy(data, domain, cond, is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_SIGNAL))
                error = ccs_write_signal_policy(data, domain, cond, is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_ARGV0))
                error = ccs_write_argv0_policy(data, domain, cond, is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_ENV))
                error = ccs_write_env_policy(data, domain, cond, is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_MOUNT))
                error = ccs_write_mount_policy(data, domain, cond, is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_UNMOUNT))
                error = ccs_write_umount_policy(data, domain, cond, is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_CHROOT))
                error = ccs_write_chroot_policy(data, domain, cond, is_delete);
        else if (ccs_str_starts(&data, KEYWORD_ALLOW_PIVOT_ROOT))
                error = ccs_write_pivot_root_policy(data, domain, cond,
                                                    is_delete);
        else
                error = ccs_write_file_policy(data, domain, cond, is_delete);
        if (cond)
                ccs_put_condition(cond);
        return error;
}

static bool ccs_print_name_union(struct ccs_io_buffer *head, bool is_group,
                                 union ccs_name_union *group)
{
        const int pos = head->read_avail;
        if (pos && head->read_buf[pos - 1] == ' ')
                head->read_avail--;
        if (is_group)
                return ccs_io_printf(head, " @%s",
                                     group->group->group_name->name);
        return ccs_io_printf(head, " %s", group->filename->name);
}

static bool ccs_print_number_union(struct ccs_io_buffer *head, bool is_group,
                                   union ccs_number_union *group)
{
        unsigned int min;
        unsigned int max;
        if (is_group)
                return ccs_io_printf(head, " @%s",
                                     group->group->group_name->name);
        min = group->value.min;
        max = group->value.max;
        if (min == max)
                return ccs_io_printf(head, " %u", min);
        return ccs_io_printf(head, " %u-%u", min, max);
}

/**
 * ccs_print_single_path_acl - Print a single path ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_single_path_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_single_path_acl(struct ccs_io_buffer *head,
                                      struct ccs_single_path_acl_record *ptr,
                                      const struct ccs_condition *cond)
{
        int pos;
        u8 bit;
        const u16 perm = ptr->perm;
        for (bit = head->read_bit; bit < MAX_SINGLE_PATH_OPERATION; bit++) {
                const char *msg;
                if (!(perm & (1 << bit)))
                        continue;
                if (head->read_execute_only && bit != TYPE_EXECUTE_ACL)
                        continue;
                /* Print "read/write" instead of "read" and "write". */
                if ((bit == TYPE_READ_ACL || bit == TYPE_WRITE_ACL)
                    && (perm & (1 << TYPE_READ_WRITE_ACL)))
                        continue;
                msg = ccs_sp2keyword(bit);
                pos = head->read_avail;
                if (!ccs_io_printf(head, "allow_%s", msg) ||
                    !ccs_print_name_union(head, ptr->name_is_group,
                                          &ptr->name) ||
                    !ccs_print_condition(head, cond))
                        goto out;
        }
        head->read_bit = 0;
        return true;
 out:
        head->read_bit = bit;
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_mkdev_acl - Print a mkdev ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_mkdev_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_mkdev_acl(struct ccs_io_buffer *head,
                                struct ccs_mkdev_acl_record *ptr,
                                const struct ccs_condition *cond)
{
        int pos;
        u8 bit;
        const u16 perm = ptr->perm;
        for (bit = head->read_bit; bit < MAX_MKDEV_OPERATION; bit++) {
                const char *msg;
                if (!(perm & (1 << bit)))
                        continue;
                msg = ccs_mkdev2keyword(bit);
                pos = head->read_avail;
                if (!ccs_io_printf(head, "allow_%s", msg) ||
                    !ccs_print_name_union(head, ptr->name_is_group,
                                          &ptr->name) ||
                    !ccs_print_number_union(head, ptr->major_is_group,
                                            &ptr->major) ||
                    !ccs_print_number_union(head, ptr->minor_is_group,
                                            &ptr->minor) ||
                    !ccs_print_condition(head, cond))
                        goto out;
        }
        head->read_bit = 0;
        return true;
 out:
        head->read_bit = bit;
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_double_path_acl - Print a double path ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_double_path_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_double_path_acl(struct ccs_io_buffer *head,
                                      struct ccs_double_path_acl_record *ptr,
                                      const struct ccs_condition *cond)
{
        int pos;
        u8 bit;
        const u8 perm = ptr->perm;
        for (bit = head->read_bit; bit < MAX_DOUBLE_PATH_OPERATION; bit++) {
                const char *msg;
                if (!(perm & (1 << bit)))
                        continue;
                msg = ccs_dp2keyword(bit);
                pos = head->read_avail;
                if (!ccs_io_printf(head, "allow_%s", msg) ||
                    !ccs_print_name_union(head, ptr->name1_is_group,
                                          &ptr->name1) ||
                    !ccs_print_name_union(head, ptr->name2_is_group,
                                          &ptr->name2) ||
                    !ccs_print_condition(head, cond))
                        goto out;
        }
        head->read_bit = 0;
        return true;
 out:
        head->read_bit = bit;
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_path_number_acl - Print an ioctl/chmod/chown/chgrp ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_path_number_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_path_number_acl(struct ccs_io_buffer *head,
                                      struct ccs_path_number_acl_record *ptr,
                                      const struct ccs_condition *cond)
{
        int pos;
        u8 bit;
        const u8 perm = ptr->perm;
        for (bit = head->read_bit; bit < MAX_PATH_NUMBER_OPERATION; bit++) {
                const char *msg;
                if (!(perm & (1 << bit)))
                        continue;
                msg = ccs_path_number2keyword(bit);
                pos = head->read_avail;
                if (!ccs_io_printf(head, "allow_%s", msg) ||
                    !ccs_print_name_union(head, ptr->name_is_group,
                                          &ptr->name) ||
                    !ccs_print_number_union(head, ptr->number_is_group,
                                            &ptr->number) ||
                    !ccs_print_condition(head, cond))
                        goto out;
        }
        head->read_bit = 0;
        return true;
 out:
        head->read_bit = bit;
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_argv0_acl - Print an argv[0] ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_argv0_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_argv0_acl(struct ccs_io_buffer *head,
                                struct ccs_argv0_acl_record *ptr,
                                const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_ARGV0 "%s %s",
                           ptr->filename->name, ptr->argv0->name))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_env_acl - Print an evironment variable name's ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_env_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_env_acl(struct ccs_io_buffer *head,
                              struct ccs_env_acl_record *ptr,
                              const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_ENV "%s", ptr->env->name))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_capability_acl - Print a capability ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_capability_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_capability_acl(struct ccs_io_buffer *head,
                                     struct ccs_capability_acl_record *ptr,
                                     const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_CAPABILITY "%s",
                           ccs_cap2keyword(ptr->operation)))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_ipv4_entry - Print IPv4 address of a network ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_ip_network_acl_record".
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_ipv4_entry(struct ccs_io_buffer *head,
                                 struct ccs_ip_network_acl_record *ptr)
{
        const u32 min_address = ptr->address.ipv4.min;
        const u32 max_address = ptr->address.ipv4.max;
        if (!ccs_io_printf(head, "%u.%u.%u.%u", HIPQUAD(min_address)))
                return false;
        if (min_address != max_address
            && !ccs_io_printf(head, "-%u.%u.%u.%u", HIPQUAD(max_address)))
                return false;
        return true;
}

/**
 * ccs_print_ipv6_entry - Print IPv6 address of a network ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_ip_network_acl_record".
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_ipv6_entry(struct ccs_io_buffer *head,
                                 struct ccs_ip_network_acl_record *ptr)
{
        char buf[64];
        const struct in6_addr *min_address = ptr->address.ipv6.min;
        const struct in6_addr *max_address = ptr->address.ipv6.max;
        ccs_print_ipv6(buf, sizeof(buf), min_address);
        if (!ccs_io_printf(head, "%s", buf))
                return false;
        if (min_address != max_address) {
                ccs_print_ipv6(buf, sizeof(buf), max_address);
                if (!ccs_io_printf(head, "-%s", buf))
                        return false;
        }
        return true;
}

/**
 * ccs_print_network_acl - Print a network ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_ip_network_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_network_acl(struct ccs_io_buffer *head,
                                  struct ccs_ip_network_acl_record *ptr,
                                  const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_NETWORK "%s ",
                           ccs_net2keyword(ptr->operation_type)))
                goto out;
        switch (ptr->record_type) {
        case IP_RECORD_TYPE_ADDRESS_GROUP:
                if (!ccs_io_printf(head, "@%s",
                                   ptr->address.group->group_name->name))
                        goto out;
                break;
        case IP_RECORD_TYPE_IPv4:
                if (!ccs_print_ipv4_entry(head, ptr))
                        goto out;
                break;
        case IP_RECORD_TYPE_IPv6:
                if (!ccs_print_ipv6_entry(head, ptr))
                        goto out;
                break;
        }
        if (!ccs_print_number_union(head, ptr->port_is_group, &ptr->port) ||
            !ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_signal_acl - Print a signal ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct signale_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_signal_acl(struct ccs_io_buffer *head,
                                 struct ccs_signal_acl_record *ptr,
                                 const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_SIGNAL "%u %s",
                           ptr->sig, ptr->domainname->name))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_execute_handler_record - Print an execute handler ACL entry.
 *
 * @head:    Pointer to "struct ccs_io_buffer".
 * @keyword: Name of the keyword.
 * @ptr:     Pointer to "struct ccs_execute_handler_record".
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_execute_handler_record(struct ccs_io_buffer *head,
                                             const char *keyword,
                                             struct ccs_execute_handler_record *
                                             ptr)
{
        return ccs_io_printf(head, "%s %s\n", keyword, ptr->handler->name);
}

/**
 * ccs_print_mount_acl - Print a mount ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_mount_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_mount_acl(struct ccs_io_buffer *head,
                                struct ccs_mount_acl_record *ptr,
                                const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_MOUNT "%s %s %s 0x%lX\n",
                           ptr->dev_name->name, ptr->dir_name->name,
                           ptr->fs_type->name, ptr->flags))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_umount_acl - Print a mount ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_umount_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_umount_acl(struct ccs_io_buffer *head,
                                 struct ccs_umount_acl_record *ptr,
                                 const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_UNMOUNT "%s\n",
                           ptr->dir->name))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_chroot_acl - Print a chroot ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_chroot_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_chroot_acl(struct ccs_io_buffer *head,
                                 struct ccs_chroot_acl_record *ptr,
                                 const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_CHROOT "%s\n",
                           ptr->dir->name))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_pivot_root_acl - Print a pivot_root ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to "struct ccs_pivot_root_acl_record".
 * @cond: Pointer to "struct ccs_condition". May be NULL.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_pivot_root_acl(struct ccs_io_buffer *head,
                                     struct ccs_pivot_root_acl_record *ptr,
                                     const struct ccs_condition *cond)
{
        int pos = head->read_avail;
        if (!ccs_io_printf(head, KEYWORD_ALLOW_PIVOT_ROOT "%s %s\n",
                           ptr->new_root->name, ptr->old_root->name))
                goto out;
        if (!ccs_print_condition(head, cond))
                goto out;
        return true;
 out:
        head->read_avail = pos;
        return false;
}

/**
 * ccs_print_entry - Print an ACL entry.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 * @ptr:  Pointer to an ACL entry.
 *
 * Returns true on success, false otherwise.
 */
static bool ccs_print_entry(struct ccs_io_buffer *head,
                            struct ccs_acl_info *ptr)
{
        const struct ccs_condition *cond = ptr->cond;
        const u8 acl_type = ccs_acl_type2(ptr);
        if (acl_type & ACL_DELETED)
                return true;
        if (acl_type == TYPE_SINGLE_PATH_ACL) {
                struct ccs_single_path_acl_record *acl
                        = container_of(ptr, struct ccs_single_path_acl_record,
                                       head);
                return ccs_print_single_path_acl(head, acl, cond);
        }
        if (acl_type == TYPE_EXECUTE_HANDLER) {
                struct ccs_execute_handler_record *acl
                        = container_of(ptr, struct ccs_execute_handler_record,
                                       head);
                const char *keyword = KEYWORD_EXECUTE_HANDLER;
                return ccs_print_execute_handler_record(head, keyword, acl);
        }
        if (acl_type == TYPE_DENIED_EXECUTE_HANDLER) {
                struct ccs_execute_handler_record *acl
                        = container_of(ptr, struct ccs_execute_handler_record,
                                       head);
                const char *keyword = KEYWORD_DENIED_EXECUTE_HANDLER;
                return ccs_print_execute_handler_record(head, keyword, acl);
        }
        if (head->read_execute_only)
                return true;
        if (acl_type == TYPE_MKDEV_ACL) {
                struct ccs_mkdev_acl_record *acl
                        = container_of(ptr, struct ccs_mkdev_acl_record, head);
                return ccs_print_mkdev_acl(head, acl, cond);
        }
        if (acl_type == TYPE_DOUBLE_PATH_ACL) {
                struct ccs_double_path_acl_record *acl
                        = container_of(ptr, struct ccs_double_path_acl_record,
                                       head);
                return ccs_print_double_path_acl(head, acl, cond);
        }
        if (acl_type == TYPE_PATH_NUMBER_ACL) {
                struct ccs_path_number_acl_record *acl
                        = container_of(ptr, struct ccs_path_number_acl_record,
                                       head);
                return ccs_print_path_number_acl(head, acl, cond);
        }
        if (acl_type == TYPE_ARGV0_ACL) {
                struct ccs_argv0_acl_record *acl
                        = container_of(ptr, struct ccs_argv0_acl_record, head);
                return ccs_print_argv0_acl(head, acl, cond);
        }
        if (acl_type == TYPE_ENV_ACL) {
                struct ccs_env_acl_record *acl
                        = container_of(ptr, struct ccs_env_acl_record, head);
                return ccs_print_env_acl(head, acl, cond);
        }
        if (acl_type == TYPE_CAPABILITY_ACL) {
                struct ccs_capability_acl_record *acl
                        = container_of(ptr, struct ccs_capability_acl_record,
                                       head);
                return ccs_print_capability_acl(head, acl, cond);
        }
        if (acl_type == TYPE_IP_NETWORK_ACL) {
                struct ccs_ip_network_acl_record *acl
                        = container_of(ptr, struct ccs_ip_network_acl_record,
                                       head);
                return ccs_print_network_acl(head, acl, cond);
        }
        if (acl_type == TYPE_SIGNAL_ACL) {
                struct ccs_signal_acl_record *acl
                        = container_of(ptr, struct ccs_signal_acl_record, head);
                return ccs_print_signal_acl(head, acl, cond);
        }
        if (acl_type == TYPE_MOUNT_ACL) {
                struct ccs_mount_acl_record *acl
                        = container_of(ptr, struct ccs_mount_acl_record, head);
                return ccs_print_mount_acl(head, acl, cond);
        }
        if (acl_type == TYPE_UMOUNT_ACL) {
                struct ccs_umount_acl_record *acl
                        = container_of(ptr, struct ccs_umount_acl_record, head);
                return ccs_print_umount_acl(head, acl, cond);
        }
        if (acl_type == TYPE_CHROOT_ACL) {
                struct ccs_chroot_acl_record *acl
                        = container_of(ptr, struct ccs_chroot_acl_record, head);
                return ccs_print_chroot_acl(head, acl, cond);
        }
        if (acl_type == TYPE_PIVOT_ROOT_ACL) {
                struct ccs_pivot_root_acl_record *acl
                        = container_of(ptr, struct ccs_pivot_root_acl_record,
                                       head);
                return ccs_print_pivot_root_acl(head, acl, cond);
        }
        /* Workaround for gcc 3.2.2's inline bug. */
        if (acl_type & ACL_DELETED)
                return true;
        BUG(); /* This must not happen. */
        return false;
}

/**
 * ccs_read_domain_policy - Read domain policy.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0.
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_read_domain_policy(struct ccs_io_buffer *head)
{
        struct list_head *dpos;
        struct list_head *apos;
        ccs_check_read_lock();
        if (head->read_eof)
                return 0;
        if (head->read_step == 0)
                head->read_step = 1;
        list_for_each_cookie(dpos, head->read_var1, &ccs_domain_list) {
                struct ccs_domain_info *domain;
                const char *quota_exceeded = "";
                const char *transition_failed = "";
                const char *ignore_global_allow_read = "";
                const char *ignore_global_allow_env = "";
                domain = list_entry(dpos, struct ccs_domain_info, list);
                if (head->read_step != 1)
                        goto acl_loop;
                if (domain->is_deleted && !head->read_single_domain)
                        continue;
                /* Print domainname and flags. */
                if (domain->quota_warned)
                        quota_exceeded = "quota_exceeded\n";
                if (domain->domain_transition_failed)
                        transition_failed = "transition_failed\n";
                if (domain->ignore_global_allow_read)
                        ignore_global_allow_read
                                = KEYWORD_IGNORE_GLOBAL_ALLOW_READ "\n";
                if (domain->ignore_global_allow_env)
                        ignore_global_allow_env
                                = KEYWORD_IGNORE_GLOBAL_ALLOW_ENV "\n";
                if (!ccs_io_printf(head, "%s\n" KEYWORD_USE_PROFILE "%u\n"
                                   "%s%s%s%s\n", domain->domainname->name,
                                   domain->profile, quota_exceeded,
                                   transition_failed,
                                   ignore_global_allow_read,
                                   ignore_global_allow_env))
                        return 0;
                head->read_step = 2;
 acl_loop:
                if (head->read_step == 3)
                        goto tail_mark;
                /* Print ACL entries in the domain. */
                list_for_each_cookie(apos, head->read_var2,
                                     &domain->acl_info_list) {
                        struct ccs_acl_info *ptr
                                = list_entry(apos, struct ccs_acl_info, list);
                        if (!ccs_print_entry(head, ptr))
                                return 0;
                }
                head->read_step = 3;
 tail_mark:
                if (!ccs_io_printf(head, "\n"))
                        return 0;
                head->read_step = 1;
                if (head->read_single_domain)
                        break;
        }
        head->read_eof = true;
        return 0;
}

/**
 * ccs_write_domain_profile - Assign profile for specified domain.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0 on success, -EINVAL otherwise.
 *
 * This is equivalent to doing
 *
 *     ( echo "select " $domainname; echo "use_profile " $profile ) |
 *     /usr/lib/ccs/loadpolicy -d
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_write_domain_profile(struct ccs_io_buffer *head)
{
        char *data = head->write_buf;
        char *cp = strchr(data, ' ');
        struct ccs_domain_info *domain;
        unsigned int profile;
        ccs_check_read_lock();
        if (!cp)
                return -EINVAL;
        *cp = '\0';
        profile = simple_strtoul(data, NULL, 10);
        if (profile >= MAX_PROFILES)
                return -EINVAL;
        domain = ccs_find_domain(cp + 1);
        if (domain && (ccs_profile_ptr[profile] || !ccs_policy_loaded))
                domain->profile = (u8) profile;
        return 0;
}

/**
 * ccs_read_domain_profile - Read only domainname and profile.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns list of profile number and domainname pairs.
 *
 * This is equivalent to doing
 *
 *     grep -A 1 '^<kernel>' /proc/ccs/domain_policy |
 *     awk ' { if ( domainname == "" ) { if ( $1 == "<kernel>" )
 *     domainname = $0; } else if ( $1 == "use_profile" ) {
 *     print $2 " " domainname; domainname = ""; } } ; '
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_read_domain_profile(struct ccs_io_buffer *head)
{
        struct list_head *pos;
        ccs_check_read_lock();
        if (head->read_eof)
                return 0;
        list_for_each_cookie(pos, head->read_var1, &ccs_domain_list) {
                struct ccs_domain_info *domain;
                domain = list_entry(pos, struct ccs_domain_info, list);
                if (domain->is_deleted)
                        continue;
                if (!ccs_io_printf(head, "%u %s\n", domain->profile,
                                   domain->domainname->name))
                        return 0;
        }
        head->read_eof = true;
        return 0;
}

/**
 * ccs_write_pid: Specify PID to obtain domainname.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0.
 */
static int ccs_write_pid(struct ccs_io_buffer *head)
{
        head->read_eof = false;
        return 0;
}

/**
 * ccs_read_pid - Read information of a process.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns the domainname which the specified PID is in or
 * process information of the specified PID on success,
 * empty string otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_read_pid(struct ccs_io_buffer *head)
{
        char *buf = head->write_buf;
        bool task_info = false;
        unsigned int pid;
        struct task_struct *p;
        struct ccs_domain_info *domain = NULL;
        u32 ccs_flags = 0;
        ccs_check_read_lock();
        /* Accessing write_buf is safe because head->io_sem is held. */
        if (!buf)
                goto done; /* Do nothing if open(O_RDONLY). */
        if (head->read_avail || head->read_eof)
                goto done;
        head->read_eof = true;
        if (ccs_str_starts(&buf, "info "))
                task_info = true;
        pid = (unsigned int) simple_strtoul(buf, NULL, 10);
        /***** CRITICAL SECTION START *****/
        read_lock(&tasklist_lock);
        p = find_task_by_pid(pid);
        if (p) {
                domain = ccs_task_domain(p);
                ccs_flags = p->ccs_flags;
        }
        read_unlock(&tasklist_lock);
        /***** CRITICAL SECTION END *****/
        if (!domain)
                goto done;
        if (!task_info)
                ccs_io_printf(head, "%u %u %s", pid, domain->profile,
                              domain->domainname->name);
        else
                ccs_io_printf(head, "%u manager=%s execute_handler=%s "
                              "state[0]=%u state[1]=%u state[2]=%u", pid,
                              ccs_flags & CCS_TASK_IS_POLICY_MANAGER ?
                              "yes" : "no",
                              ccs_flags & CCS_TASK_IS_EXECUTE_HANDLER ?
                              "yes" : "no",
                              (u8) (ccs_flags >> 24),
                              (u8) (ccs_flags >> 16),
                              (u8) (ccs_flags >> 8));
 done:
        return 0;
}

/**
 * ccs_write_exception_policy - Write exception policy.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int ccs_write_exception_policy(struct ccs_io_buffer *head)
{
        char *data = head->write_buf;
        bool is_delete = ccs_str_starts(&data, KEYWORD_DELETE);
        if (ccs_str_starts(&data, KEYWORD_KEEP_DOMAIN))
                return ccs_write_domain_keeper_policy(data, false, is_delete);
        if (ccs_str_starts(&data, KEYWORD_NO_KEEP_DOMAIN))
                return ccs_write_domain_keeper_policy(data, true, is_delete);
        if (ccs_str_starts(&data, KEYWORD_INITIALIZE_DOMAIN))
                return ccs_write_domain_initializer_policy(data, false,
                                                           is_delete);
        if (ccs_str_starts(&data, KEYWORD_NO_INITIALIZE_DOMAIN))
                return ccs_write_domain_initializer_policy(data, true,
                                                           is_delete);
        if (ccs_str_starts(&data, KEYWORD_AGGREGATOR))
                return ccs_write_aggregator_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_ALLOW_READ))
                return ccs_write_globally_readable_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_ALLOW_ENV))
                return ccs_write_globally_usable_env_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_FILE_PATTERN))
                return ccs_write_pattern_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_PATH_GROUP))
                return ccs_write_path_group_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_NUMBER_GROUP))
                return ccs_write_number_group_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_DENY_REWRITE))
                return ccs_write_no_rewrite_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_ADDRESS_GROUP))
                return ccs_write_address_group_policy(data, is_delete);
        if (ccs_str_starts(&data, KEYWORD_DENY_AUTOBIND))
                return ccs_write_reserved_port_policy(data, is_delete);
        return -EINVAL;
}

/**
 * ccs_read_exception_policy - Read exception policy.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0 on success, -EINVAL otherwise.
 *
 * Caller holds ccs_read_lock().
 */
static int ccs_read_exception_policy(struct ccs_io_buffer *head)
{
        ccs_check_read_lock();
        if (!head->read_eof) {
                switch (head->read_step) {
                case 0:
                        head->read_var2 = NULL;
                        head->read_step = 1;
                case 1:
                        if (!ccs_read_domain_keeper_policy(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 2;
                case 2:
                        if (!ccs_read_globally_readable_policy(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 3;
                case 3:
                        if (!ccs_read_globally_usable_env_policy(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 4;
                case 4:
                        if (!ccs_read_domain_initializer_policy(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 6;
                case 6:
                        if (!ccs_read_aggregator_policy(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 7;
                case 7:
                        if (!ccs_read_file_pattern(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 8;
                case 8:
                        if (!ccs_read_no_rewrite_policy(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 9;
                case 9:
                        if (!ccs_read_path_group_policy(head))
                                break;
                        head->read_var1 = NULL;
                        head->read_var2 = NULL;
                        head->read_step = 10;
                case 10:
                        if (!ccs_read_number_group_policy(head))
                                break;
                        head->read_var1 = NULL;
                        head->read_var2 = NULL;
                        head->read_step = 11;
                case 11:
                        if (!ccs_read_address_group_policy(head))
                                break;
                        head->read_var2 = NULL;
                        head->read_step = 12;
                case 12:
                        if (!ccs_read_reserved_port_policy(head))
                                break;
                        head->read_eof = true;
                        break;
                default:
                        return -EINVAL;
                }
        }
        return 0;
}

/* Wait queue for ccs_query_list. */
static DECLARE_WAIT_QUEUE_HEAD(ccs_query_wait);

/* Lock for manipulating ccs_query_list. */
static DEFINE_SPINLOCK(ccs_query_list_lock);

/* Structure for query. */
struct ccs_query_entry {
        struct list_head list;
        char *query;
        int query_len;
        unsigned int serial;
        int timer;
        int answer;
};

/* The list for "struct ccs_query_entry". */
static LIST_HEAD(ccs_query_list);

/* Number of "struct file" referring /proc/ccs/query interface. */
static atomic_t ccs_query_observers = ATOMIC_INIT(0);

/**
 * ccs_check_supervisor - Ask for the supervisor's decision.
 *
 * @r:       Pointer to "struct ccs_request_info".
 * @fmt:     The printf()'s format string, followed by parameters.
 *
 * Returns 0 if the supervisor decided to permit the access request which
 * violated the policy in enforcing mode, 1 if the supervisor decided to
 * retry the access request which violated the policy in enforcing mode,
 * -EPERM otherwise.
 */
int ccs_check_supervisor(struct ccs_request_info *r, const char *fmt, ...)
{
        va_list args;
        int error = -EPERM;
        int pos;
        int len;
        static unsigned int ccs_serial;
        struct ccs_query_entry *ccs_query_entry = NULL;
        bool quota_exceeded = false;
        char *header;
        if (!r->domain)
                r->domain = ccs_current_domain();
        if (!atomic_read(&ccs_query_observers)) {
                int i;
                if (current->ccs_flags & CCS_DONT_SLEEP_ON_ENFORCE_ERROR)
                        return -EPERM;
                for (i = 0; i < ccs_check_flags(r->domain, CCS_SLEEP_PERIOD);
                     i++) {
                        set_current_state(TASK_INTERRUPTIBLE);
                        schedule_timeout(HZ / 10);
                }
                return -EPERM;
        }
        va_start(args, fmt);
        len = vsnprintf((char *) &pos, sizeof(pos) - 1, fmt, args) + 32;
        va_end(args);
        header = ccs_init_audit_log(&len, r);
        if (!header)
                goto out;
        ccs_query_entry = kzalloc(sizeof(*ccs_query_entry), GFP_KERNEL);
        if (!ccs_query_entry)
                goto out;
        ccs_query_entry->query = kzalloc(len, GFP_KERNEL);
        if (!ccs_query_entry->query)
                goto out;
        INIT_LIST_HEAD(&ccs_query_entry->list);
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_query_list_lock);
        if (ccs_quota_for_query && ccs_query_memory_size + len +
            sizeof(*ccs_query_entry) >= ccs_quota_for_query) {
                quota_exceeded = true;
        } else {
                ccs_query_memory_size += len + sizeof(*ccs_query_entry);
                ccs_query_entry->serial = ccs_serial++;
        }
        spin_unlock(&ccs_query_list_lock);
        /***** CRITICAL SECTION END *****/
        if (quota_exceeded)
                goto out;
        pos = snprintf(ccs_query_entry->query, len - 1, "Q%u-%hu\n%s",
                       ccs_query_entry->serial, r->retry, header);
        kfree(header);
        header = NULL;
        va_start(args, fmt);
        vsnprintf(ccs_query_entry->query + pos, len - 1 - pos, fmt, args);
        ccs_query_entry->query_len = strlen(ccs_query_entry->query) + 1;
        va_end(args);
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_query_list_lock);
        list_add_tail(&ccs_query_entry->list, &ccs_query_list);
        spin_unlock(&ccs_query_list_lock);
        /***** CRITICAL SECTION END *****/
        /* Give 10 seconds for supervisor's opinion. */
        for (ccs_query_entry->timer = 0;
             atomic_read(&ccs_query_observers) && ccs_query_entry->timer < 100;
             ccs_query_entry->timer++) {
                wake_up(&ccs_query_wait);
                set_current_state(TASK_INTERRUPTIBLE);
                schedule_timeout(HZ / 10);
                if (ccs_query_entry->answer)
                        break;
        }
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_query_list_lock);
        list_del(&ccs_query_entry->list);
        ccs_query_memory_size -= len + sizeof(*ccs_query_entry);
        spin_unlock(&ccs_query_list_lock);
        /***** CRITICAL SECTION END *****/
        switch (ccs_query_entry->answer) {
        case 3: /* Asked to retry by administrator. */
                error = 1;
                r->retry++;
                break;
        case 1:
                /* Granted by administrator. */
                error = 0;
                break;
        case 0:
                /* Timed out. */
                break;
        default:
                /* Rejected by administrator. */
                break;
        }
 out:
        if (ccs_query_entry)
                kfree(ccs_query_entry->query);
        kfree(ccs_query_entry);
        kfree(header);
        return error;
}

/**
 * ccs_poll_query - poll() for /proc/ccs/query.
 *
 * @file: Pointer to "struct file".
 * @wait: Pointer to "poll_table".
 *
 * Returns POLLIN | POLLRDNORM when ready to read, 0 otherwise.
 *
 * Waits for access requests which violated policy in enforcing mode.
 */
static int ccs_poll_query(struct file *file, poll_table *wait)
{
        struct list_head *tmp;
        bool found = false;
        u8 i;
        for (i = 0; i < 2; i++) {
                /***** CRITICAL SECTION START *****/
                spin_lock(&ccs_query_list_lock);
                list_for_each(tmp, &ccs_query_list) {
                        struct ccs_query_entry *ptr
                                = list_entry(tmp, struct ccs_query_entry, list);
                        if (ptr->answer)
                                continue;
                        found = true;
                        break;
                }
                spin_unlock(&ccs_query_list_lock);
                /***** CRITICAL SECTION END *****/
                if (found)
                        return POLLIN | POLLRDNORM;
                if (i)
                        break;
                poll_wait(file, &ccs_query_wait, wait);
        }
        return 0;
}

/**
 * ccs_read_query - Read access requests which violated policy in enforcing mode.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0.
 */
static int ccs_read_query(struct ccs_io_buffer *head)
{
        struct list_head *tmp;
        int pos = 0;
        int len = 0;
        char *buf;
        if (head->read_avail)
                return 0;
        if (head->read_buf) {
                kfree(head->read_buf);
                head->read_buf = NULL;
                head->readbuf_size = 0;
        }
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_query_list_lock);
        list_for_each(tmp, &ccs_query_list) {
                struct ccs_query_entry *ptr
                        = list_entry(tmp, struct ccs_query_entry, list);
                if (ptr->answer)
                        continue;
                if (pos++ != head->read_step)
                        continue;
                len = ptr->query_len;
                break;
        }
        spin_unlock(&ccs_query_list_lock);
        /***** CRITICAL SECTION END *****/
        if (!len) {
                head->read_step = 0;
                return 0;
        }
        buf = kzalloc(len, GFP_KERNEL);
        if (!buf)
                return 0;
        pos = 0;
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_query_list_lock);
        list_for_each(tmp, &ccs_query_list) {
                struct ccs_query_entry *ptr
                        = list_entry(tmp, struct ccs_query_entry, list);
                if (ptr->answer)
                        continue;
                if (pos++ != head->read_step)
                        continue;
                /*
                 * Some query can be skipped because ccs_query_list
                 * can change, but I don't care.
                 */
                if (len == ptr->query_len)
                        memmove(buf, ptr->query, len);
                break;
        }
        spin_unlock(&ccs_query_list_lock);
        /***** CRITICAL SECTION END *****/
        if (buf[0]) {
                head->read_avail = len;
                head->readbuf_size = head->read_avail;
                head->read_buf = buf;
                head->read_step++;
        } else {
                kfree(buf);
        }
        return 0;
}

/**
 * ccs_write_answer - Write the supervisor's decision.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0 on success, -EINVAL otherwise.
 */
static int ccs_write_answer(struct ccs_io_buffer *head)
{
        char *data = head->write_buf;
        struct list_head *tmp;
        unsigned int serial;
        unsigned int answer;
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_query_list_lock);
        list_for_each(tmp, &ccs_query_list) {
                struct ccs_query_entry *ptr
                        = list_entry(tmp, struct ccs_query_entry, list);
                ptr->timer = 0;
        }
        spin_unlock(&ccs_query_list_lock);
        /***** CRITICAL SECTION END *****/
        if (sscanf(data, "A%u=%u", &serial, &answer) != 2)
                return -EINVAL;
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_query_list_lock);
        list_for_each(tmp, &ccs_query_list) {
                struct ccs_query_entry *ptr
                        = list_entry(tmp, struct ccs_query_entry, list);
                if (ptr->serial != serial)
                        continue;
                if (!ptr->answer)
                        ptr->answer = answer;
                break;
        }
        spin_unlock(&ccs_query_list_lock);
        /***** CRITICAL SECTION END *****/
        return 0;
}

/**
 * ccs_read_version: Get version.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns version information.
 */
static int ccs_read_version(struct ccs_io_buffer *head)
{
        if (!head->read_eof) {
                ccs_io_printf(head, "1.7.0-pre");
                head->read_eof = true;
        }
        return 0;
}

/**
 * ccs_read_self_domain - Get the current process's domainname.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns the current process's domainname.
 */
static int ccs_read_self_domain(struct ccs_io_buffer *head)
{
        if (!head->read_eof) {
                /*
                 * ccs_current_domain()->domainname != NULL
                 * because every process belongs to a domain and
                 * the domain's name cannot be NULL.
                 */
                ccs_io_printf(head, "%s",
                              ccs_current_domain()->domainname->name);
                head->read_eof = true;
        }
        return 0;
}

/**
 * ccs_open_control - open() for /proc/ccs/ interface.
 *
 * @type: Type of interface.
 * @file: Pointer to "struct file".
 *
 * Associates policy handler and returns 0 on success, -ENOMEM otherwise.
 */
int ccs_open_control(const u8 type, struct file *file)
{
        struct ccs_io_buffer *head = kzalloc(sizeof(*head), GFP_KERNEL);
        if (!head)
                return -ENOMEM;
        mutex_init(&head->io_sem);
        head->type = type;
        switch (type) {
        case CCS_DOMAINPOLICY: /* /proc/ccs/domain_policy */
                head->write = ccs_write_domain_policy;
                head->read = ccs_read_domain_policy;
                break;
        case CCS_EXCEPTIONPOLICY: /* /proc/ccs/exception_policy */
                head->write = ccs_write_exception_policy;
                head->read = ccs_read_exception_policy;
                break;
#ifdef CONFIG_CCSECURITY_AUDIT
        case CCS_GRANTLOG: /* /proc/ccs/grant_log */
                head->poll = ccs_poll_grant_log;
                head->read = ccs_read_grant_log;
                break;
        case CCS_REJECTLOG: /* /proc/ccs/reject_log */
                head->poll = ccs_poll_reject_log;
                head->read = ccs_read_reject_log;
                break;
#endif
        case CCS_SELFDOMAIN: /* /proc/ccs/self_domain */
                head->read = ccs_read_self_domain;
                break;
        case CCS_DOMAIN_STATUS: /* /proc/ccs/.domain_status */
                head->write = ccs_write_domain_profile;
                head->read = ccs_read_domain_profile;
                break;
        case CCS_EXECUTE_HANDLER: /* /proc/ccs/.execute_handler */
                /* Allow execute_handler to read process's status. */
                if (!(current->ccs_flags & CCS_TASK_IS_EXECUTE_HANDLER)) {
                        kfree(head);
                        return -EPERM;
                }
                /* fall through */
        case CCS_PROCESS_STATUS: /* /proc/ccs/.process_status */
                head->write = ccs_write_pid;
                head->read = ccs_read_pid;
                break;
        case CCS_VERSION: /* /proc/ccs/version */
                head->read = ccs_read_version;
                head->readbuf_size = 128;
                break;
        case CCS_MEMINFO: /* /proc/ccs/meminfo */
                head->write = ccs_write_memory_quota;
                head->read = ccs_read_memory_counter;
                head->readbuf_size = 512;
                break;
        case CCS_PROFILE: /* /proc/ccs/profile */
                head->write = ccs_write_profile;
                head->read = ccs_read_profile;
                break;
        case CCS_QUERY: /* /proc/ccs/query */
                head->poll = ccs_poll_query;
                head->write = ccs_write_answer;
                head->read = ccs_read_query;
                break;
        case CCS_MANAGER: /* /proc/ccs/manager */
                head->write = ccs_write_manager_policy;
                head->read = ccs_read_manager_policy;
                break;
        }
        if (!(file->f_mode & FMODE_READ)) {
                /*
                 * No need to allocate read_buf since it is not opened
                 * for reading.
                 */
                head->read = NULL;
                head->poll = NULL;
        } else if (type != CCS_QUERY &&
                   type != CCS_GRANTLOG && type != CCS_REJECTLOG) {
                /*
                 * Don't allocate buffer for reading if the file is one of
                 * /proc/ccs/grant_log , /proc/ccs/reject_log , /proc/ccs/query.
                 */
                if (!head->readbuf_size)
                        head->readbuf_size = 4096 * 2;
                head->read_buf = kzalloc(head->readbuf_size, GFP_KERNEL);
                if (!head->read_buf) {
                        kfree(head);
                        return -ENOMEM;
                }
        }
        if (!(file->f_mode & FMODE_WRITE)) {
                /*
                 * No need to allocate write_buf since it is not opened
                 * for writing.
                 */
                head->write = NULL;
        } else if (head->write) {
                head->writebuf_size = 4096 * 2;
                head->write_buf = kzalloc(head->writebuf_size, GFP_KERNEL);
                if (!head->write_buf) {
                        kfree(head->read_buf);
                        kfree(head);
                        return -ENOMEM;
                }
        }
        if (type != CCS_QUERY &&
            type != CCS_GRANTLOG && type != CCS_REJECTLOG)
                head->reader_idx = ccs_read_lock();
        file->private_data = head;
        /*
         * Call the handler now if the file is /proc/ccs/self_domain
         * so that the user can use "cat < /proc/ccs/self_domain" to
         * know the current process's domainname.
         */
        if (type == CCS_SELFDOMAIN)
                ccs_read_control(file, NULL, 0);
        /*
         * If the file is /proc/ccs/query , increment the observer counter.
         * The obserber counter is used by ccs_check_supervisor() to see if
         * there is some process monitoring /proc/ccs/query.
         */
        else if (type == CCS_QUERY)
                atomic_inc(&ccs_query_observers);
        return 0;
}

/**
 * ccs_poll_control - poll() for /proc/ccs/ interface.
 *
 * @file: Pointer to "struct file".
 * @wait: Pointer to "poll_table".
 *
 * Waits for read readiness.
 * /proc/ccs/query is handled by /usr/lib/ccs/ccs-queryd and
 * /proc/ccs/grant_log and /proc/ccs/reject_log are handled by
 * /usr/lib/ccs/ccs-auditd.
 */
int ccs_poll_control(struct file *file, poll_table *wait)
{
        struct ccs_io_buffer *head = file->private_data;
        if (!head->poll)
                return -ENOSYS;
        return head->poll(file, wait);
}

/**
 * ccs_read_control - read() for /proc/ccs/ interface.
 *
 * @file:       Pointer to "struct file".
 * @buffer:     Poiner to buffer to write to.
 * @buffer_len: Size of @buffer.
 *
 * Returns bytes read on success, negative value otherwise.
 */
int ccs_read_control(struct file *file, char __user *buffer,
                     const int buffer_len)
{
        int len = 0;
        struct ccs_io_buffer *head = file->private_data;
        char *cp;
        if (!head->read)
                return -ENOSYS;
        if (!access_ok(VERIFY_WRITE, buffer, buffer_len))
                return -EFAULT;
        if (mutex_lock_interruptible(&head->io_sem))
                return -EINTR;
        /* Call the policy handler. */
        len = head->read(head);
        if (len < 0)
                goto out;
        /* Write to buffer. */
        len = head->read_avail;
        if (len > buffer_len)
                len = buffer_len;
        if (!len)
                goto out;
        /* head->read_buf changes by some functions. */
        cp = head->read_buf;
        if (copy_to_user(buffer, cp, len)) {
                len = -EFAULT;
                goto out;
        }
        head->read_avail -= len;
        memmove(cp, cp + len, head->read_avail);
 out:
        mutex_unlock(&head->io_sem);
        return len;
}

/**
 * ccs_write_control - write() for /proc/ccs/ interface.
 *
 * @file:       Pointer to "struct file".
 * @buffer:     Pointer to buffer to read from.
 * @buffer_len: Size of @buffer.
 *
 * Returns @buffer_len on success, negative value otherwise.
 */
int ccs_write_control(struct file *file, const char __user *buffer,
                      const int buffer_len)
{
        struct ccs_io_buffer *head = file->private_data;
        int error = buffer_len;
        int avail_len = buffer_len;
        char *cp0 = head->write_buf;
        if (!head->write)
                return -ENOSYS;
        if (!access_ok(VERIFY_READ, buffer, buffer_len))
                return -EFAULT;
        /* Don't allow updating policies by non manager programs. */
        if (head->write != ccs_write_pid &&
            head->write != ccs_write_domain_policy &&
            !ccs_is_policy_manager())
                return -EPERM;
        if (mutex_lock_interruptible(&head->io_sem))
                return -EINTR;
        /* Read a line and dispatch it to the policy handler. */
        while (avail_len > 0) {
                char c;
                if (head->write_avail >= head->writebuf_size - 1) {
                        error = -ENOMEM;
                        break;
                } else if (get_user(c, buffer)) {
                        error = -EFAULT;
                        break;
                }
                buffer++;
                avail_len--;
                cp0[head->write_avail++] = c;
                if (c != '\n')
                        continue;
                cp0[head->write_avail - 1] = '\0';
                head->write_avail = 0;
                ccs_normalize_line(cp0);
                head->write(head);
        }
        mutex_unlock(&head->io_sem);
        return error;
}

/**
 * ccs_close_control - close() for /proc/ccs/ interface.
 *
 * @file: Pointer to "struct file".
 *
 * Releases memory and returns 0.
 */
int ccs_close_control(struct file *file)
{
        struct ccs_io_buffer *head = file->private_data;
        const bool is_write = head->write_buf != NULL;
        const u8 type = head->type;
        /*
         * If the file is /proc/ccs/query , decrement the observer counter.
         */
        if (type == CCS_QUERY)
                atomic_dec(&ccs_query_observers);
        if (type != CCS_QUERY &&
            type != CCS_GRANTLOG && type != CCS_REJECTLOG)
                ccs_read_unlock(head->reader_idx);
        /* Release memory used for policy I/O. */
        kfree(head->read_buf);
        head->read_buf = NULL;
        kfree(head->write_buf);
        head->write_buf = NULL;
        kfree(head);
        head = NULL;
        file->private_data = NULL;
        if (is_write)
                ccs_run_gc();
        return 0;
}