acl.c

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/*
 * linux/fs/ext2/acl.c
 *
 * Copyright (C) 2001-2003 Andreas Gruenbacher, <[email protected]>
 */

#include <linux/capability.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"

/*
 * Convert from filesystem to in-memory representation.
 */
static struct posix_acl *
ext2_acl_from_disk(const void *value, size_t size)
{
    const char *end = (char *)value + size;
    int n, count;
    struct posix_acl *acl;

    if (!value)
        return NULL;
    if (size < sizeof(ext2_acl_header))
         return ERR_PTR(-EINVAL);
    if (((ext2_acl_header *)value)->a_version !=
        cpu_to_le32(EXT2_ACL_VERSION))
        return ERR_PTR(-EINVAL);
    value = (char *)value + sizeof(ext2_acl_header);
    count = ext2_acl_count(size);
    if (count < 0)
        return ERR_PTR(-EINVAL);
    if (count == 0)
        return NULL;
    acl = posix_acl_alloc(count, GFP_KERNEL);
    if (!acl)
        return ERR_PTR(-ENOMEM);
    for (n=0; n < count; n++) {
        ext2_acl_entry *entry =
            (ext2_acl_entry *)value;
        if ((char *)value + sizeof(ext2_acl_entry_short) > end)
            goto fail;
        acl->a_entries[n].e_tag  = le16_to_cpu(entry->e_tag);
        acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
        switch(acl->a_entries[n].e_tag) {
            case ACL_USER_OBJ:
            case ACL_GROUP_OBJ:
            case ACL_MASK:
            case ACL_OTHER:
                value = (char *)value +
                    sizeof(ext2_acl_entry_short);
                break;

            case ACL_USER:
                value = (char *)value + sizeof(ext2_acl_entry);
                if ((char *)value > end)
                    goto fail;
                acl->a_entries[n].e_uid =
                    make_kuid(&init_user_ns,
                          le32_to_cpu(entry->e_id));
                break;
            case ACL_GROUP:
                value = (char *)value + sizeof(ext2_acl_entry);
                if ((char *)value > end)
                    goto fail;
                acl->a_entries[n].e_gid =
                    make_kgid(&init_user_ns,
                          le32_to_cpu(entry->e_id));
                break;

            default:
                goto fail;
        }
    }
    if (value != end)
        goto fail;
    return acl;

fail:
    posix_acl_release(acl);
    return ERR_PTR(-EINVAL);
}

/*
 * Convert from in-memory to filesystem representation.
 */
static void *
ext2_acl_to_disk(const struct posix_acl *acl, size_t *size)
{
    ext2_acl_header *ext_acl;
    char *e;
    size_t n;

    *size = ext2_acl_size(acl->a_count);
    ext_acl = kmalloc(sizeof(ext2_acl_header) + acl->a_count *
            sizeof(ext2_acl_entry), GFP_KERNEL);
    if (!ext_acl)
        return ERR_PTR(-ENOMEM);
    ext_acl->a_version = cpu_to_le32(EXT2_ACL_VERSION);
    e = (char *)ext_acl + sizeof(ext2_acl_header);
    for (n=0; n < acl->a_count; n++) {
        const struct posix_acl_entry *acl_e = &acl->a_entries[n];
        ext2_acl_entry *entry = (ext2_acl_entry *)e;
        entry->e_tag  = cpu_to_le16(acl_e->e_tag);
        entry->e_perm = cpu_to_le16(acl_e->e_perm);
        switch(acl_e->e_tag) {
            case ACL_USER:
                entry->e_id = cpu_to_le32(
                    from_kuid(&init_user_ns, acl_e->e_uid));
                e += sizeof(ext2_acl_entry);
                break;
            case ACL_GROUP:
                entry->e_id = cpu_to_le32(
                    from_kgid(&init_user_ns, acl_e->e_gid));
                e += sizeof(ext2_acl_entry);
                break;

            case ACL_USER_OBJ:
            case ACL_GROUP_OBJ:
            case ACL_MASK:
            case ACL_OTHER:
                e += sizeof(ext2_acl_entry_short);
                break;

            default:
                goto fail;
        }
    }
    return (char *)ext_acl;

fail:
    kfree(ext_acl);
    return ERR_PTR(-EINVAL);
}

/*
 * inode->i_mutex: don't care
 */
struct posix_acl *
ext2_get_acl(struct inode *inode, int type)
{
    int name_index;
    char *value = NULL;
    struct posix_acl *acl;
    int retval;

    if (!test_opt(inode->i_sb, POSIX_ACL))
        return NULL;

    acl = get_cached_acl(inode, type);
    if (acl != ACL_NOT_CACHED)
        return acl;

    switch (type) {
    case ACL_TYPE_ACCESS:
        name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
        break;
    case ACL_TYPE_DEFAULT:
        name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
        break;
    default:
        BUG();
    }
    retval = ext2_xattr_get(inode, name_index, "", NULL, 0);
    if (retval > 0) {
        value = kmalloc(retval, GFP_KERNEL);
        if (!value)
            return ERR_PTR(-ENOMEM);
        retval = ext2_xattr_get(inode, name_index, "", value, retval);
    }
    if (retval > 0)
        acl = ext2_acl_from_disk(value, retval);
    else if (retval == -ENODATA || retval == -ENOSYS)
        acl = NULL;
    else
        acl = ERR_PTR(retval);
    kfree(value);

    if (!IS_ERR(acl))
        set_cached_acl(inode, type, acl);

    return acl;
}

/*
 * inode->i_mutex: down
 */
static int
ext2_set_acl(struct inode *inode, int type, struct posix_acl *acl)
{
    int name_index;
    void *value = NULL;
    size_t size = 0;
    int error;

    if (S_ISLNK(inode->i_mode))
        return -EOPNOTSUPP;
    if (!test_opt(inode->i_sb, POSIX_ACL))
        return 0;

    switch(type) {
        case ACL_TYPE_ACCESS:
            name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
            if (acl) {
                error = posix_acl_equiv_mode(acl, &inode->i_mode);
                if (error < 0)
                    return error;
                else {
                    inode->i_ctime = CURRENT_TIME_SEC;
                    mark_inode_dirty(inode);
                    if (error == 0)
                        acl = NULL;
                }
            }
            break;

        case ACL_TYPE_DEFAULT:
            name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
            if (!S_ISDIR(inode->i_mode))
                return acl ? -EACCES : 0;
            break;

        default:
            return -EINVAL;
    }
    if (acl) {
        value = ext2_acl_to_disk(acl, &size);
        if (IS_ERR(value))
            return (int)PTR_ERR(value);
    }

    error = ext2_xattr_set(inode, name_index, "", value, size, 0);

    kfree(value);
    if (!error)
        set_cached_acl(inode, type, acl);
    return error;
}

/*
 * Initialize the ACLs of a new inode. Called from ext2_new_inode.
 *
 * dir->i_mutex: down
 * inode->i_mutex: up (access to inode is still exclusive)
 */
int
ext2_init_acl(struct inode *inode, struct inode *dir)
{
    struct posix_acl *acl = NULL;
    int error = 0;

    if (!S_ISLNK(inode->i_mode)) {
        if (test_opt(dir->i_sb, POSIX_ACL)) {
            acl = ext2_get_acl(dir, ACL_TYPE_DEFAULT);
            if (IS_ERR(acl))
                return PTR_ERR(acl);
        }
        if (!acl)
            inode->i_mode &= ~current_umask();
    }
    if (test_opt(inode->i_sb, POSIX_ACL) && acl) {
        if (S_ISDIR(inode->i_mode)) {
            error = ext2_set_acl(inode, ACL_TYPE_DEFAULT, acl);
            if (error)
                goto cleanup;
        }
        error = posix_acl_create(&acl, GFP_KERNEL, &inode->i_mode);
        if (error < 0)
            return error;
        if (error > 0) {
            /* This is an extended ACL */
            error = ext2_set_acl(inode, ACL_TYPE_ACCESS, acl);
        }
    }
cleanup:
       posix_acl_release(acl);
       return error;
}

/*
 * Does chmod for an inode that may have an Access Control List. The
 * inode->i_mode field must be updated to the desired value by the caller
 * before calling this function.
 * Returns 0 on success, or a negative error number.
 *
 * We change the ACL rather than storing some ACL entries in the file
 * mode permission bits (which would be more efficient), because that
 * would break once additional permissions (like  ACL_APPEND, ACL_DELETE
 * for directories) are added. There are no more bits available in the
 * file mode.
 *
 * inode->i_mutex: down
 */
int
ext2_acl_chmod(struct inode *inode)
{
    struct posix_acl *acl;
        int error;

    if (!test_opt(inode->i_sb, POSIX_ACL))
        return 0;
    if (S_ISLNK(inode->i_mode))
        return -EOPNOTSUPP;
    acl = ext2_get_acl(inode, ACL_TYPE_ACCESS);
    if (IS_ERR(acl) || !acl)
        return PTR_ERR(acl);
    error = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
    if (error)
        return error;
    error = ext2_set_acl(inode, ACL_TYPE_ACCESS, acl);
    posix_acl_release(acl);
    return error;
}

/*
 * Extended attribut handlers
 */
static size_t
ext2_xattr_list_acl_access(struct dentry *dentry, char *list, size_t list_size,
               const char *name, size_t name_len, int type)
{
    const size_t size = sizeof(POSIX_ACL_XATTR_ACCESS);

    if (!test_opt(dentry->d_sb, POSIX_ACL))
        return 0;
    if (list && size <= list_size)
        memcpy(list, POSIX_ACL_XATTR_ACCESS, size);
    return size;
}

static size_t
ext2_xattr_list_acl_default(struct dentry *dentry, char *list, size_t list_size,
                const char *name, size_t name_len, int type)
{
    const size_t size = sizeof(POSIX_ACL_XATTR_DEFAULT);

    if (!test_opt(dentry->d_sb, POSIX_ACL))
        return 0;
    if (list && size <= list_size)
        memcpy(list, POSIX_ACL_XATTR_DEFAULT, size);
    return size;
}

static int
ext2_xattr_get_acl(struct dentry *dentry, const char *name, void *buffer,
           size_t size, int type)
{
    struct posix_acl *acl;
    int error;

    if (strcmp(name, "") != 0)
        return -EINVAL;
    if (!test_opt(dentry->d_sb, POSIX_ACL))
        return -EOPNOTSUPP;

    acl = ext2_get_acl(dentry->d_inode, type);
    if (IS_ERR(acl))
        return PTR_ERR(acl);
    if (acl == NULL)
        return -ENODATA;
    error = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
    posix_acl_release(acl);

    return error;
}

static int
ext2_xattr_set_acl(struct dentry *dentry, const char *name, const void *value,
           size_t size, int flags, int type)
{
    struct posix_acl *acl;
    int error;

    if (strcmp(name, "") != 0)
        return -EINVAL;
    if (!test_opt(dentry->d_sb, POSIX_ACL))
        return -EOPNOTSUPP;
    if (!inode_owner_or_capable(dentry->d_inode))
        return -EPERM;

    if (value) {
        acl = posix_acl_from_xattr(&init_user_ns, value, size);
        if (IS_ERR(acl))
            return PTR_ERR(acl);
        else if (acl) {
            error = posix_acl_valid(acl);
            if (error)
                goto release_and_out;
        }
    } else
        acl = NULL;

    error = ext2_set_acl(dentry->d_inode, type, acl);

release_and_out:
    posix_acl_release(acl);
    return error;
}

const struct xattr_handler ext2_xattr_acl_access_handler = {
    .prefix = POSIX_ACL_XATTR_ACCESS,
    .flags  = ACL_TYPE_ACCESS,
    .list   = ext2_xattr_list_acl_access,
    .get    = ext2_xattr_get_acl,
    .set    = ext2_xattr_set_acl,
};

const struct xattr_handler ext2_xattr_acl_default_handler = {
    .prefix = POSIX_ACL_XATTR_DEFAULT,
    .flags  = ACL_TYPE_DEFAULT,
    .list   = ext2_xattr_list_acl_default,
    .get    = ext2_xattr_get_acl,
    .set    = ext2_xattr_set_acl,
};