linux/fs/btrfs/xattr.c
Goldwyn Rodrigues b51111271b btrfs: check if root is readonly while setting security xattr
For a filesystem which has btrfs read-only property set to true, all
write operations including xattr should be denied. However, security
xattr can still be changed even if btrfs ro property is true.

This happens because xattr_permission() does not have any restrictions
on security.*, system.*  and in some cases trusted.* from VFS and
the decision is left to the underlying filesystem. See comments in
xattr_permission() for more details.

This patch checks if the root is read-only before performing the set
xattr operation.

Testcase:

  DEV=/dev/vdb
  MNT=/mnt

  mkfs.btrfs -f $DEV
  mount $DEV $MNT
  echo "file one" > $MNT/f1

  setfattr -n "security.one" -v 2 $MNT/f1
  btrfs property set /mnt ro true

  setfattr -n "security.one" -v 1 $MNT/f1

  umount $MNT

CC: stable@vger.kernel.org # 4.9+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2022-08-22 18:06:30 +02:00

493 lines
13 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2007 Red Hat. All rights reserved.
*/
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/rwsem.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/posix_acl_xattr.h>
#include <linux/iversion.h>
#include <linux/sched/mm.h>
#include "ctree.h"
#include "btrfs_inode.h"
#include "transaction.h"
#include "xattr.h"
#include "disk-io.h"
#include "props.h"
#include "locking.h"
int btrfs_getxattr(struct inode *inode, const char *name,
void *buffer, size_t size)
{
struct btrfs_dir_item *di;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_path *path;
struct extent_buffer *leaf;
int ret = 0;
unsigned long data_ptr;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
/* lookup the xattr by name */
di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
name, strlen(name), 0);
if (!di) {
ret = -ENODATA;
goto out;
} else if (IS_ERR(di)) {
ret = PTR_ERR(di);
goto out;
}
leaf = path->nodes[0];
/* if size is 0, that means we want the size of the attr */
if (!size) {
ret = btrfs_dir_data_len(leaf, di);
goto out;
}
/* now get the data out of our dir_item */
if (btrfs_dir_data_len(leaf, di) > size) {
ret = -ERANGE;
goto out;
}
/*
* The way things are packed into the leaf is like this
* |struct btrfs_dir_item|name|data|
* where name is the xattr name, so security.foo, and data is the
* content of the xattr. data_ptr points to the location in memory
* where the data starts in the in memory leaf
*/
data_ptr = (unsigned long)((char *)(di + 1) +
btrfs_dir_name_len(leaf, di));
read_extent_buffer(leaf, buffer, data_ptr,
btrfs_dir_data_len(leaf, di));
ret = btrfs_dir_data_len(leaf, di);
out:
btrfs_free_path(path);
return ret;
}
int btrfs_setxattr(struct btrfs_trans_handle *trans, struct inode *inode,
const char *name, const void *value, size_t size, int flags)
{
struct btrfs_dir_item *di = NULL;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_path *path;
size_t name_len = strlen(name);
int ret = 0;
ASSERT(trans);
if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
return -ENOSPC;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
path->skip_release_on_error = 1;
if (!value) {
di = btrfs_lookup_xattr(trans, root, path,
btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
if (!di && (flags & XATTR_REPLACE))
ret = -ENODATA;
else if (IS_ERR(di))
ret = PTR_ERR(di);
else if (di)
ret = btrfs_delete_one_dir_name(trans, root, path, di);
goto out;
}
/*
* For a replace we can't just do the insert blindly.
* Do a lookup first (read-only btrfs_search_slot), and return if xattr
* doesn't exist. If it exists, fall down below to the insert/replace
* path - we can't race with a concurrent xattr delete, because the VFS
* locks the inode's i_mutex before calling setxattr or removexattr.
*/
if (flags & XATTR_REPLACE) {
ASSERT(inode_is_locked(inode));
di = btrfs_lookup_xattr(NULL, root, path,
btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
if (!di)
ret = -ENODATA;
else if (IS_ERR(di))
ret = PTR_ERR(di);
if (ret)
goto out;
btrfs_release_path(path);
di = NULL;
}
ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
name, name_len, value, size);
if (ret == -EOVERFLOW) {
/*
* We have an existing item in a leaf, split_leaf couldn't
* expand it. That item might have or not a dir_item that
* matches our target xattr, so lets check.
*/
ret = 0;
btrfs_assert_tree_write_locked(path->nodes[0]);
di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
if (!di && !(flags & XATTR_REPLACE)) {
ret = -ENOSPC;
goto out;
}
} else if (ret == -EEXIST) {
ret = 0;
di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
ASSERT(di); /* logic error */
} else if (ret) {
goto out;
}
if (di && (flags & XATTR_CREATE)) {
ret = -EEXIST;
goto out;
}
if (di) {
/*
* We're doing a replace, and it must be atomic, that is, at
* any point in time we have either the old or the new xattr
* value in the tree. We don't want readers (getxattr and
* listxattrs) to miss a value, this is specially important
* for ACLs.
*/
const int slot = path->slots[0];
struct extent_buffer *leaf = path->nodes[0];
const u16 old_data_len = btrfs_dir_data_len(leaf, di);
const u32 item_size = btrfs_item_size(leaf, slot);
const u32 data_size = sizeof(*di) + name_len + size;
unsigned long data_ptr;
char *ptr;
if (size > old_data_len) {
if (btrfs_leaf_free_space(leaf) <
(size - old_data_len)) {
ret = -ENOSPC;
goto out;
}
}
if (old_data_len + name_len + sizeof(*di) == item_size) {
/* No other xattrs packed in the same leaf item. */
if (size > old_data_len)
btrfs_extend_item(path, size - old_data_len);
else if (size < old_data_len)
btrfs_truncate_item(path, data_size, 1);
} else {
/* There are other xattrs packed in the same item. */
ret = btrfs_delete_one_dir_name(trans, root, path, di);
if (ret)
goto out;
btrfs_extend_item(path, data_size);
}
ptr = btrfs_item_ptr(leaf, slot, char);
ptr += btrfs_item_size(leaf, slot) - data_size;
di = (struct btrfs_dir_item *)ptr;
btrfs_set_dir_data_len(leaf, di, size);
data_ptr = ((unsigned long)(di + 1)) + name_len;
write_extent_buffer(leaf, value, data_ptr, size);
btrfs_mark_buffer_dirty(leaf);
} else {
/*
* Insert, and we had space for the xattr, so path->slots[0] is
* where our xattr dir_item is and btrfs_insert_xattr_item()
* filled it.
*/
}
out:
btrfs_free_path(path);
if (!ret) {
set_bit(BTRFS_INODE_COPY_EVERYTHING,
&BTRFS_I(inode)->runtime_flags);
clear_bit(BTRFS_INODE_NO_XATTRS, &BTRFS_I(inode)->runtime_flags);
}
return ret;
}
/*
* @value: "" makes the attribute to empty, NULL removes it
*/
int btrfs_setxattr_trans(struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_trans_handle *trans;
const bool start_trans = (current->journal_info == NULL);
int ret;
if (start_trans) {
/*
* 1 unit for inserting/updating/deleting the xattr
* 1 unit for the inode item update
*/
trans = btrfs_start_transaction(root, 2);
if (IS_ERR(trans))
return PTR_ERR(trans);
} else {
/*
* This can happen when smack is enabled and a directory is being
* created. It happens through d_instantiate_new(), which calls
* smack_d_instantiate(), which in turn calls __vfs_setxattr() to
* set the transmute xattr (XATTR_NAME_SMACKTRANSMUTE) on the
* inode. We have already reserved space for the xattr and inode
* update at btrfs_mkdir(), so just use the transaction handle.
* We don't join or start a transaction, as that will reset the
* block_rsv of the handle and trigger a warning for the start
* case.
*/
ASSERT(strncmp(name, XATTR_SECURITY_PREFIX,
XATTR_SECURITY_PREFIX_LEN) == 0);
trans = current->journal_info;
}
ret = btrfs_setxattr(trans, inode, name, value, size, flags);
if (ret)
goto out;
inode_inc_iversion(inode);
inode->i_ctime = current_time(inode);
ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
if (ret)
btrfs_abort_transaction(trans, ret);
out:
if (start_trans)
btrfs_end_transaction(trans);
return ret;
}
ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
struct btrfs_key found_key;
struct btrfs_key key;
struct inode *inode = d_inode(dentry);
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_path *path;
int iter_ret = 0;
int ret = 0;
size_t total_size = 0, size_left = size;
/*
* ok we want all objects associated with this id.
* NOTE: we set key.offset = 0; because we want to start with the
* first xattr that we find and walk forward
*/
key.objectid = btrfs_ino(BTRFS_I(inode));
key.type = BTRFS_XATTR_ITEM_KEY;
key.offset = 0;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
path->reada = READA_FORWARD;
/* search for our xattrs */
btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
struct extent_buffer *leaf;
int slot;
struct btrfs_dir_item *di;
u32 item_size;
u32 cur;
leaf = path->nodes[0];
slot = path->slots[0];
/* check to make sure this item is what we want */
if (found_key.objectid != key.objectid)
break;
if (found_key.type > BTRFS_XATTR_ITEM_KEY)
break;
if (found_key.type < BTRFS_XATTR_ITEM_KEY)
continue;
di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
item_size = btrfs_item_size(leaf, slot);
cur = 0;
while (cur < item_size) {
u16 name_len = btrfs_dir_name_len(leaf, di);
u16 data_len = btrfs_dir_data_len(leaf, di);
u32 this_len = sizeof(*di) + name_len + data_len;
unsigned long name_ptr = (unsigned long)(di + 1);
total_size += name_len + 1;
/*
* We are just looking for how big our buffer needs to
* be.
*/
if (!size)
goto next;
if (!buffer || (name_len + 1) > size_left) {
iter_ret = -ERANGE;
break;
}
read_extent_buffer(leaf, buffer, name_ptr, name_len);
buffer[name_len] = '\0';
size_left -= name_len + 1;
buffer += name_len + 1;
next:
cur += this_len;
di = (struct btrfs_dir_item *)((char *)di + this_len);
}
}
if (iter_ret < 0)
ret = iter_ret;
else
ret = total_size;
btrfs_free_path(path);
return ret;
}
static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
struct dentry *unused, struct inode *inode,
const char *name, void *buffer, size_t size)
{
name = xattr_full_name(handler, name);
return btrfs_getxattr(inode, name, buffer, size);
}
static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
struct user_namespace *mnt_userns,
struct dentry *unused, struct inode *inode,
const char *name, const void *buffer,
size_t size, int flags)
{
if (btrfs_root_readonly(BTRFS_I(inode)->root))
return -EROFS;
name = xattr_full_name(handler, name);
return btrfs_setxattr_trans(inode, name, buffer, size, flags);
}
static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
struct user_namespace *mnt_userns,
struct dentry *unused, struct inode *inode,
const char *name, const void *value,
size_t size, int flags)
{
int ret;
struct btrfs_trans_handle *trans;
struct btrfs_root *root = BTRFS_I(inode)->root;
name = xattr_full_name(handler, name);
ret = btrfs_validate_prop(BTRFS_I(inode), name, value, size);
if (ret)
return ret;
if (btrfs_ignore_prop(BTRFS_I(inode), name))
return 0;
trans = btrfs_start_transaction(root, 2);
if (IS_ERR(trans))
return PTR_ERR(trans);
ret = btrfs_set_prop(trans, inode, name, value, size, flags);
if (!ret) {
inode_inc_iversion(inode);
inode->i_ctime = current_time(inode);
ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
if (ret)
btrfs_abort_transaction(trans, ret);
}
btrfs_end_transaction(trans);
return ret;
}
static const struct xattr_handler btrfs_security_xattr_handler = {
.prefix = XATTR_SECURITY_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set,
};
static const struct xattr_handler btrfs_trusted_xattr_handler = {
.prefix = XATTR_TRUSTED_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set,
};
static const struct xattr_handler btrfs_user_xattr_handler = {
.prefix = XATTR_USER_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set,
};
static const struct xattr_handler btrfs_btrfs_xattr_handler = {
.prefix = XATTR_BTRFS_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set_prop,
};
const struct xattr_handler *btrfs_xattr_handlers[] = {
&btrfs_security_xattr_handler,
#ifdef CONFIG_BTRFS_FS_POSIX_ACL
&posix_acl_access_xattr_handler,
&posix_acl_default_xattr_handler,
#endif
&btrfs_trusted_xattr_handler,
&btrfs_user_xattr_handler,
&btrfs_btrfs_xattr_handler,
NULL,
};
static int btrfs_initxattrs(struct inode *inode,
const struct xattr *xattr_array, void *fs_private)
{
struct btrfs_trans_handle *trans = fs_private;
const struct xattr *xattr;
unsigned int nofs_flag;
char *name;
int err = 0;
/*
* We're holding a transaction handle, so use a NOFS memory allocation
* context to avoid deadlock if reclaim happens.
*/
nofs_flag = memalloc_nofs_save();
for (xattr = xattr_array; xattr->name != NULL; xattr++) {
name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
strlen(xattr->name) + 1, GFP_KERNEL);
if (!name) {
err = -ENOMEM;
break;
}
strcpy(name, XATTR_SECURITY_PREFIX);
strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
err = btrfs_setxattr(trans, inode, name, xattr->value,
xattr->value_len, 0);
kfree(name);
if (err < 0)
break;
}
memalloc_nofs_restore(nofs_flag);
return err;
}
int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
struct inode *inode, struct inode *dir,
const struct qstr *qstr)
{
return security_inode_init_security(inode, dir, qstr,
&btrfs_initxattrs, trans);
}