security/ccsecurity/realpath.c

/*
 * fs/realpath.c
 *
 * Get the canonicalized absolute pathnames. The basis for SAKURA and TOMOYO.
 *
 * Copyright (C) 2005-2009  NTT DATA CORPORATION
 *
 * Version: 1.6.7   2009/04/01
 *
 * This file is applicable to both 2.4.30 and 2.6.11 and later.
 * See README.ccs for ChangeLog.
 *
 */
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/utime.h>
#include <linux/file.h>
#include <linux/smp_lock.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/atomic.h>
#include <linux/version.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 0)
#include <linux/namei.h>
#include <linux/mount.h>
static const int ccs_lookup_flags = LOOKUP_FOLLOW;
#else
static const int ccs_lookup_flags = LOOKUP_FOLLOW | LOOKUP_POSITIVE;
#endif
#include <linux/realpath.h>
#include <linux/proc_fs.h>
#include <linux/ccs_common.h>
#include <net/sock.h>

/**
 * ccs_get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
 *
 * @dentry: Pointer to "struct dentry".
 * @vfsmnt: Pointer to "struct vfsmount".
 * @buffer: Pointer to buffer to return value in.
 * @buflen: Sizeof @buffer.
 *
 * Returns 0 on success, -ENOMEM otherwise.
 *
 * Caller holds the dcache_lock and vfsmount_lock.
 * Based on __d_path() in fs/dcache.c
 *
 * If dentry is a directory, trailing '/' is appended.
 * Characters out of 0x20 < c < 0x7F range are converted to
 * \ooo style octal string.
 * Character \ is converted to \\ string.
 */
static int ccs_get_absolute_path(struct dentry *dentry, struct vfsmount *vfsmnt,
                                 char *buffer, int buflen)
{
        /***** CRITICAL SECTION START *****/
        char *start = buffer;
        char *end = buffer + buflen;
        bool is_dir = (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode));

        if (buflen < 256)
                goto out;

        *--end = '\0';
        buflen--;

        for (;;) {
                struct dentry *parent;

                if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
                        /* Global root? */
                        if (vfsmnt->mnt_parent == vfsmnt)
                                break;
                        dentry = vfsmnt->mnt_mountpoint;
                        vfsmnt = vfsmnt->mnt_parent;
                        continue;
                }
                if (is_dir) {
                        is_dir = false;
                        *--end = '/';
                        buflen--;
                }
                parent = dentry->d_parent;
                {
                        const char *sp = dentry->d_name.name;
                        const char *cp = sp + dentry->d_name.len - 1;
                        unsigned char c;

                        /*
                         * Exception: Use /proc/self/ rather than
                         * /proc/\$/ for current process.
                         */
                        if (IS_ROOT(parent) && *sp > '0' && *sp <= '9' &&
                            parent->d_sb &&
                            parent->d_sb->s_magic == PROC_SUPER_MAGIC) {
                                char *ep;
                                const pid_t pid
                                        = (pid_t) simple_strtoul(sp, &ep, 10);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
                                const pid_t tgid
                                        = task_tgid_nr_ns(current,
                                                          dentry->d_sb->
                                                          s_fs_info);
                                if (!*ep && pid == tgid && tgid) {
                                        sp = "self";
                                        cp = sp + 3;
                                }
#else
                                if (!*ep && pid == sys_getpid()) {
                                        sp = "self";
                                        cp = sp + 3;
                                }
#endif
                        }

                        while (sp <= cp) {
                                c = *(unsigned char *) cp;
                                if (c == '\\') {
                                        buflen -= 2;
                                        if (buflen < 0)
                                                goto out;
                                        *--end = '\\';
                                        *--end = '\\';
                                } else if (c > ' ' && c < 127) {
                                        if (--buflen < 0)
                                                goto out;
                                        *--end = (char) c;
                                } else {
                                        buflen -= 4;
                                        if (buflen < 0)
                                                goto out;
                                        *--end = (c & 7) + '0';
                                        *--end = ((c >> 3) & 7) + '0';
                                        *--end = (c >> 6) + '0';
                                        *--end = '\\';
                                }
                                cp--;
                        }
                        if (--buflen < 0)
                                goto out;
                        *--end = '/';
                }
                dentry = parent;
        }
        if (*end == '/') {
                buflen++;
                end++;
        }
        {
                const char *sp = dentry->d_name.name;
                const char *cp = sp + dentry->d_name.len - 1;
                unsigned char c;
                while (sp <= cp) {
                        c = *(unsigned char *) cp;
                        if (c == '\\') {
                                buflen -= 2;
                                if (buflen < 0)
                                        goto out;
                                *--end = '\\';
                                *--end = '\\';
                        } else if (c > ' ' && c < 127) {
                                if (--buflen < 0)
                                        goto out;
                                *--end = (char) c;
                        } else {
                                buflen -= 4;
                                if (buflen < 0)
                                        goto out;
                                *--end = (c & 7) + '0';
                                *--end = ((c >> 3) & 7) + '0';
                                *--end = (c >> 6) + '0';
                                *--end = '\\';
                        }
                        cp--;
                }
        }
        /* Move the pathname to the top of the buffer. */
        memmove(start, end, strlen(end) + 1);
        return 0;
 out:
        return -ENOMEM;
        /***** CRITICAL SECTION END *****/
}

#define SOCKFS_MAGIC 0x534F434B

/**
 * ccs_realpath_from_dentry2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
 *
 * @dentry:      Pointer to "struct dentry".
 * @mnt:         Pointer to "struct vfsmount".
 * @newname:     Pointer to buffer to return value in.
 * @newname_len: Size of @newname.
 *
 * Returns 0 on success, negative value otherwise.
 */
int ccs_realpath_from_dentry2(struct dentry *dentry, struct vfsmount *mnt,
                              char *newname, int newname_len)
{
        int error = -EINVAL;
        struct dentry *d_dentry;
        struct vfsmount *d_mnt;
        if (!dentry || !newname || newname_len <= 2048)
                goto out;
        /* Get better name for socket. */
        if (dentry->d_sb && dentry->d_sb->s_magic == SOCKFS_MAGIC) {
                struct inode *inode = dentry->d_inode;
                struct socket *sock = inode ? SOCKET_I(inode) : NULL;
                struct sock *sk = sock ? sock->sk : NULL;
                if (sk) {
                        snprintf(newname, newname_len - 1,
                                 "socket:[family=%u:type=%u:protocol=%u]",
                                 sk->sk_family, sk->sk_type, sk->sk_protocol);
                } else {
                        snprintf(newname, newname_len - 1, "socket:[unknown]");
                }
                return 0;
        }
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 22)
        if (dentry->d_op && dentry->d_op->d_dname) {
                /* For "socket:[\$]" and "pipe:[\$]". */
                static const int offset = 1536;
                char *dp = newname;
                char *sp = dentry->d_op->d_dname(dentry, newname + offset,
                                                 newname_len - offset);
                if (IS_ERR(sp)) {
                        error = PTR_ERR(sp);
                        goto out;
                }
                error = -ENOMEM;
                newname += offset;
                while (1) {
                        const unsigned char c = *(unsigned char *) sp++;
                        if (c == '\\') {
                                if (dp + 2 >= newname)
                                        break;
                                *dp++ = '\\';
                                *dp++ = '\\';
                        } else if (c > ' ' && c < 127) {
                                if (dp + 1 >= newname)
                                        break;
                                *dp++ = (char) c;
                        } else if (c) {
                                if (dp + 4 >= newname)
                                        break;
                                *dp++ = '\\';
                                *dp++ = (c >> 6) + '0';
                                *dp++ = ((c >> 3) & 7) + '0';
                                *dp++ = (c & 7) + '0';
                        } else {
                                *dp = '\0';
                                return 0;
                        }
                }
                goto out;
        }
#endif
        if (!mnt)
                goto out;
        d_dentry = dget(dentry);
        d_mnt = mntget(mnt);
        /***** CRITICAL SECTION START *****/
        ccs_realpath_lock();
        error = ccs_get_absolute_path(d_dentry, d_mnt, newname, newname_len);
        ccs_realpath_unlock();
        /***** CRITICAL SECTION END *****/
        dput(d_dentry);
        mntput(d_mnt);
 out:
        if (error)
                printk(KERN_WARNING "ccs_realpath: Pathname too long. (%d)\n",
                       error);
        return error;
}

/**
 * ccs_realpath_from_dentry - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 *
 * @dentry: Pointer to "struct dentry".
 * @mnt:    Pointer to "struct vfsmount".
 *
 * Returns the realpath of the given @dentry and @mnt on success,
 * NULL otherwise.
 *
 * These functions use ccs_alloc(), so caller must ccs_free()
 * if these functions didn't return NULL.
 */
char *ccs_realpath_from_dentry(struct dentry *dentry, struct vfsmount *mnt)
{
        char *buf = ccs_alloc(CCS_MAX_PATHNAME_LEN, false);
        if (buf && ccs_realpath_from_dentry2(dentry, mnt, buf,
                                             CCS_MAX_PATHNAME_LEN - 1) == 0)
                return buf;
        ccs_free(buf);
        return NULL;
}

/**
 * ccs_realpath - Get realpath of a pathname.
 *
 * @pathname: The pathname to solve.
 *
 * Returns the realpath of @pathname on success, NULL otherwise.
 */
char *ccs_realpath(const char *pathname)
{
        struct nameidata nd;
        if (pathname && path_lookup(pathname, ccs_lookup_flags, &nd) == 0) {
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
                char *buf = ccs_realpath_from_dentry(nd.path.dentry,
                                                     nd.path.mnt);
                path_put(&nd.path);
#else
                char *buf = ccs_realpath_from_dentry(nd.dentry, nd.mnt);
                path_release(&nd);
#endif
                return buf;
        }
        return NULL;
}

/**
 * ccs_realpath_both - Get realpath of a pathname and symlink.
 *
 * @pathname: The pathname to solve.
 * @ee:       Pointer to "struct ccs_execve_entry".
 *
 * Returns 0 on success, negative value otherwise.
 */
int ccs_realpath_both(const char *pathname, struct ccs_execve_entry *ee)
{
        struct nameidata nd;
        int ret;
        bool is_symlink;
        if (!pathname ||
            path_lookup(pathname, ccs_lookup_flags ^ LOOKUP_FOLLOW, &nd))
                return -ENOENT;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
        is_symlink = nd.path.dentry->d_inode &&
                S_ISLNK(nd.path.dentry->d_inode->i_mode);
        ret = ccs_realpath_from_dentry2(nd.path.dentry, nd.path.mnt,
                                        ee->tmp, CCS_EXEC_TMPSIZE - 1);
        path_put(&nd.path);
#else
        is_symlink = nd.dentry->d_inode && S_ISLNK(nd.dentry->d_inode->i_mode);
        ret = ccs_realpath_from_dentry2(nd.dentry, nd.mnt, ee->tmp,
                                        CCS_EXEC_TMPSIZE - 1);
        path_release(&nd);
#endif
        if (ret)
                return -ENOMEM;
        if (strlen(ee->tmp) > CCS_MAX_PATHNAME_LEN - 1)
                return -ENOMEM;
        ee->program_path[CCS_MAX_PATHNAME_LEN - 1] = '\0';
        if (!is_symlink) {
                strncpy(ee->program_path, ee->tmp,
                        CCS_MAX_PATHNAME_LEN - 1);
                return 0;
        }
        if (path_lookup(pathname, ccs_lookup_flags, &nd))
                return -ENOENT;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
        ret = ccs_realpath_from_dentry2(nd.path.dentry, nd.path.mnt,
                                        ee->program_path,
                                        CCS_MAX_PATHNAME_LEN - 1);
        path_put(&nd.path);
#else
        ret = ccs_realpath_from_dentry2(nd.dentry, nd.mnt, ee->program_path,
                                        CCS_MAX_PATHNAME_LEN - 1);
        path_release(&nd);
#endif
        return ret ? -ENOMEM : 0;
}

/**
 * ccs_round_up - Round up an integer so that the returned pointers are appropriately aligned.
 *
 * @size: Size in bytes.
 *
 * Returns rounded value of @size.
 *
 * FIXME: Are there more requirements that is needed for assigning value
 * atomically?
 */
static inline unsigned int ccs_round_up(const unsigned int size)
{
        if (sizeof(void *) >= sizeof(long))
                return ((size + sizeof(void *) - 1)
                        / sizeof(void *)) * sizeof(void *);
        else
                return ((size + sizeof(long) - 1)
                        / sizeof(long)) * sizeof(long);
}

static unsigned int ccs_allocated_memory_for_elements;
static unsigned int ccs_quota_for_elements;

/**
 * ccs_alloc_element - Allocate permanent memory for structures.
 *
 * @size: Size in bytes.
 *
 * Returns pointer to allocated memory on success, NULL otherwise.
 *
 * The RAM is chunked, so NEVER try to kfree() the returned pointer.
 */
void *ccs_alloc_element(const unsigned int size)
{
        static DEFINE_MUTEX(lock);
        static char *ccs_buf;
        static unsigned int ccs_buf_used_len = PAGE_SIZE;
        char *ptr = NULL;
        const unsigned int word_aligned_size = ccs_round_up(size);
        if (word_aligned_size > PAGE_SIZE)
                return NULL;
        mutex_lock(&lock);
        if (ccs_buf_used_len + word_aligned_size > PAGE_SIZE) {
                if (!ccs_quota_for_elements || ccs_allocated_memory_for_elements
                    + PAGE_SIZE <= ccs_quota_for_elements)
                        ptr = kzalloc(PAGE_SIZE, GFP_KERNEL);
                if (!ptr) {
                        printk(KERN_WARNING "ERROR: Out of memory "
                               "for ccs_alloc_element().\n");
                        if (!ccs_policy_loaded)
                                panic("MAC Initialization failed.\n");
                } else {
                        ccs_buf = ptr;
                        ccs_allocated_memory_for_elements += PAGE_SIZE;
                        ccs_buf_used_len = word_aligned_size;
                }
        } else if (word_aligned_size) {
                int i;
                ptr = ccs_buf + ccs_buf_used_len;
                ccs_buf_used_len += word_aligned_size;
                for (i = 0; i < word_aligned_size; i++) {
                        if (!ptr[i])
                                continue;
                        printk(KERN_ERR "WARNING: Reserved memory was tainted! "
                               "The system might go wrong.\n");
                        ptr[i] = '\0';
                }
        }
        mutex_unlock(&lock);
        return ptr;
}

static unsigned int ccs_allocated_memory_for_savename;
static unsigned int ccs_quota_for_savename;

#define MAX_HASH 256

/* Structure for string data. */
struct ccs_name_entry {
        struct list1_head list;
        struct ccs_path_info entry;
};

/* Structure for available memory region. */
struct ccs_free_memory_block_list {
        struct list_head list;
        char *ptr;             /* Pointer to a free area. */
        int len;               /* Length of the area.     */
};

/* The list for "struct ccs_name_entry". */
static struct list1_head ccs_name_list[MAX_HASH];

/**
 * ccs_save_name - Allocate permanent memory for string data.
 *
 * @name: The string to store into the permernent memory.
 *
 * Returns pointer to "struct ccs_path_info" on success, NULL otherwise.
 *
 * The RAM is shared, so NEVER try to modify or kfree() the returned name.
 */
const struct ccs_path_info *ccs_save_name(const char *name)
{
        static LIST_HEAD(ccs_fmb_list);
        static DEFINE_MUTEX(lock);
        struct ccs_name_entry *ptr;
        unsigned int hash;
        struct ccs_free_memory_block_list *fmb;
        int len;
        char *cp;
        if (!name)
                return NULL;
        len = strlen(name) + 1;
        if (len > CCS_MAX_PATHNAME_LEN) {
                printk(KERN_WARNING "ERROR: Name too long "
                       "for ccs_save_name().\n");
                return NULL;
        }
        hash = full_name_hash((const unsigned char *) name, len - 1);
        mutex_lock(&lock);
        list1_for_each_entry(ptr, &ccs_name_list[hash % MAX_HASH], list) {
                if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
                        goto out;
        }
        list_for_each_entry(fmb, &ccs_fmb_list, list) {
                if (len <= fmb->len)
                        goto ready;
        }
        if (!ccs_quota_for_savename ||
            ccs_allocated_memory_for_savename + PAGE_SIZE
            <= ccs_quota_for_savename)
                cp = kzalloc(PAGE_SIZE, GFP_KERNEL);
        else
                cp = NULL;
        fmb = kzalloc(sizeof(*fmb), GFP_KERNEL);
        if (!cp || !fmb) {
                kfree(cp);
                kfree(fmb);
                printk(KERN_WARNING "ERROR: Out of memory "
                       "for ccs_save_name().\n");
                if (!ccs_policy_loaded)
                        panic("MAC Initialization failed.\n");
                ptr = NULL;
                goto out;
        }
        ccs_allocated_memory_for_savename += PAGE_SIZE;
        list_add(&fmb->list, &ccs_fmb_list);
        fmb->ptr = cp;
        fmb->len = PAGE_SIZE;
 ready:
        ptr = ccs_alloc_element(sizeof(*ptr));
        if (!ptr)
                goto out;
        ptr->entry.name = fmb->ptr;
        memmove(fmb->ptr, name, len);
        ccs_fill_path_info(&ptr->entry);
        fmb->ptr += len;
        fmb->len -= len;
        list1_add_tail_mb(&ptr->list, &ccs_name_list[hash % MAX_HASH]);
        if (fmb->len == 0) {
                list_del(&fmb->list);
                kfree(fmb);
        }
 out:
        mutex_unlock(&lock);
        return ptr ? &ptr->entry : NULL;
}

/* Structure for temporarily allocated memory. */
struct ccs_cache_entry {
        struct list_head list;
        void *ptr;
        int size;
};

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 20)
static struct kmem_cache *ccs_cachep;
#else
static kmem_cache_t *ccs_cachep;
#endif

/**
 * ccs_realpath_init - Initialize realpath related code.
 *
 * Returns 0.
 */
static int __init ccs_realpath_init(void)
{
        int i;
        /* Constraint for ccs_save_name(). */
        if (CCS_MAX_PATHNAME_LEN > PAGE_SIZE)
                panic("Bad size.");
        /* Constraint for "struct ccs_execve_entry"->tmp users. */
        if (CCS_MAX_PATHNAME_LEN > CCS_EXEC_TMPSIZE)
                panic("Bad size.");
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 23)
        ccs_cachep = kmem_cache_create("ccs_cache",
                                       sizeof(struct ccs_cache_entry),
                                       0, 0, NULL);
#else
        ccs_cachep = kmem_cache_create("ccs_cache",
                                       sizeof(struct ccs_cache_entry),
                                       0, 0, NULL, NULL);
#endif
        if (!ccs_cachep)
                panic("Can't create cache.\n");
        for (i = 0; i < MAX_HASH; i++)
                INIT_LIST1_HEAD(&ccs_name_list[i]);
        INIT_LIST1_HEAD(&ccs_kernel_domain.acl_info_list);
        ccs_kernel_domain.domainname = ccs_save_name(ROOT_NAME);
        list1_add_tail_mb(&ccs_kernel_domain.list, &ccs_domain_list);
        if (ccs_find_domain(ROOT_NAME) != &ccs_kernel_domain)
                panic("Can't register ccs_kernel_domain");
#ifdef CONFIG_TOMOYO_BUILTIN_INITIALIZERS
        {
                /* Load built-in policy. */
                static char ccs_builtin_initializers[] __initdata
                        = CONFIG_TOMOYO_BUILTIN_INITIALIZERS;
                char *cp = ccs_builtin_initializers;
                ccs_normalize_line(cp);
                while (cp && *cp) {
                        char *cp2 = strchr(cp, ' ');
                        if (cp2)
                                *cp2++ = '\0';
                        ccs_write_domain_initializer_policy(cp, false, false);
                        cp = cp2;
                }
        }
#endif
        return 0;
}

#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 5, 0)
__initcall(ccs_realpath_init);
#else
core_initcall(ccs_realpath_init);
#endif

/* The list for "struct ccs_cache_entry". */
static LIST_HEAD(ccs_audit_cache_list);
static LIST_HEAD(ccs_acl_cache_list);
static DEFINE_SPINLOCK(ccs_cache_list_lock);

static unsigned int ccs_dynamic_memory_size;
static unsigned int ccs_quota_for_dynamic;

#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 5, 0)
/**
 * ccs_round2 - Rounded up to power-of-two value.
 *
 * @size: Size in bytes.
 *
 * Returns power-of-two of @size.
 */
static int ccs_round2(size_t size)
{
#if PAGE_SIZE == 4096
        size_t bsize = 32;
#else
        size_t bsize = 64;
#endif
        while (size > bsize)
                bsize <<= 1;
        return bsize;
}
#endif

/**
 * ccs_alloc - Allocate memory for temporary purpose.
 *
 * @size: Size in bytes.
 *
 * Returns pointer to allocated memory on success, NULL otherwise.
 */
void *ccs_alloc(const size_t size, const _Bool check_quota)
{
        struct ccs_cache_entry *new_entry;
        void *ret = kzalloc(size, GFP_KERNEL);
        if (!ret)
                goto out;
        new_entry = kmem_cache_alloc(ccs_cachep, GFP_KERNEL);
        if (!new_entry) {
                kfree(ret);
                ret = NULL;
                goto out;
        }
        INIT_LIST_HEAD(&new_entry->list);
        new_entry->ptr = ret;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 0)
        new_entry->size = ksize(ret);
#else
        new_entry->size = ccs_round2(size);
#endif
        if (check_quota) {
                bool quota_exceeded = false;
                /***** CRITICAL SECTION START *****/
                spin_lock(&ccs_cache_list_lock);
                if (!ccs_quota_for_dynamic ||
                    ccs_dynamic_memory_size + new_entry->size
                    <= ccs_quota_for_dynamic) {
                        list_add_tail(&new_entry->list, &ccs_audit_cache_list);
                        ccs_dynamic_memory_size += new_entry->size;
                } else {
                        quota_exceeded = true;
                }
                spin_unlock(&ccs_cache_list_lock);
                /***** CRITICAL SECTION END *****/
                if (quota_exceeded) {
                        kfree(ret);
                        kmem_cache_free(ccs_cachep, new_entry);
                        ret = NULL;
                }
        } else {
                /***** CRITICAL SECTION START *****/
                spin_lock(&ccs_cache_list_lock);
                list_add(&new_entry->list, &ccs_acl_cache_list);
                ccs_dynamic_memory_size += new_entry->size;
                spin_unlock(&ccs_cache_list_lock);
                /***** CRITICAL SECTION END *****/
        }
 out:
        return ret;
}

/**
 * ccs_free - Release memory allocated by ccs_alloc().
 *
 * @p: Pointer returned by ccs_alloc(). May be NULL.
 *
 * Returns nothing.
 */
void ccs_free(const void *p)
{
        struct list_head *v;
        struct ccs_cache_entry *entry = NULL;
        if (!p)
                return;
        /***** CRITICAL SECTION START *****/
        spin_lock(&ccs_cache_list_lock);
        list_for_each(v, &ccs_acl_cache_list) {
                entry = list_entry(v, struct ccs_cache_entry, list);
                if (entry->ptr == p)
                        break;
                entry = NULL;
        }
        if (!entry) {
                list_for_each(v, &ccs_audit_cache_list) {
                        entry = list_entry(v, struct ccs_cache_entry, list);
                        if (entry->ptr == p)
                                break;
                        entry = NULL;
                }
        }
        if (entry) {
                list_del(&entry->list);
                ccs_dynamic_memory_size -= entry->size;
        }
        spin_unlock(&ccs_cache_list_lock);
        /***** CRITICAL SECTION END *****/
        if (entry) {
                kfree(p);
                kmem_cache_free(ccs_cachep, entry);
        } else {
                printk(KERN_WARNING "BUG: ccs_free() with invalid pointer.\n");
        }
}

/**
 * ccs_read_memory_counter - Check for memory usage.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns memory usage.
 */
int ccs_read_memory_counter(struct ccs_io_buffer *head)
{
        if (!head->read_eof) {
                const unsigned int shared = ccs_allocated_memory_for_savename;
                const unsigned int private = ccs_allocated_memory_for_elements;
                const unsigned int dynamic = ccs_dynamic_memory_size;
                char buffer[64];
                memset(buffer, 0, sizeof(buffer));
                if (ccs_quota_for_savename)
                        snprintf(buffer, sizeof(buffer) - 1,
                                 "   (Quota: %10u)", ccs_quota_for_savename);
                else
                        buffer[0] = '\0';
                ccs_io_printf(head, "Shared:  %10u%s\n", shared, buffer);
                if (ccs_quota_for_elements)
                        snprintf(buffer, sizeof(buffer) - 1,
                                 "   (Quota: %10u)", ccs_quota_for_elements);
                else
                        buffer[0] = '\0';
                ccs_io_printf(head, "Private: %10u%s\n", private, buffer);
                if (ccs_quota_for_dynamic)
                        snprintf(buffer, sizeof(buffer) - 1,
                                 "   (Quota: %10u)", ccs_quota_for_dynamic);
                else
                        buffer[0] = '\0';
                ccs_io_printf(head, "Dynamic: %10u%s\n", dynamic, buffer);
                ccs_io_printf(head, "Total:   %10u\n",
                              shared + private + dynamic);
                head->read_eof = true;
        }
        return 0;
}

/**
 * ccs_write_memory_quota - Set memory quota.
 *
 * @head: Pointer to "struct ccs_io_buffer".
 *
 * Returns 0.
 */
int ccs_write_memory_quota(struct ccs_io_buffer *head)
{
        char *data = head->write_buf;
        unsigned int size;
        if (sscanf(data, "Shared: %u", &size) == 1)
                ccs_quota_for_savename = size;
        else if (sscanf(data, "Private: %u", &size) == 1)
                ccs_quota_for_elements = size;
        else if (sscanf(data, "Dynamic: %u", &size) == 1)
                ccs_quota_for_dynamic = size;
        return 0;
}