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linux/fs/btrfs/disk-io.h
Qu Wenruo 2ba48b2004 btrfs: fix compat_ro checks against remount 
[BUG]
Even with commit 81d5d61454 ("btrfs: enhance unsupported compat RO
flags handling"), btrfs can still mount a fs with unsupported compat_ro
flags read-only, then remount it RW:

  # btrfs ins dump-super /dev/loop0 | grep compat_ro_flags -A 3
  compat_ro_flags		0x403
			( FREE_SPACE_TREE |
			  FREE_SPACE_TREE_VALID |
			  unknown flag: 0x400 )

  # mount /dev/loop0 /mnt/btrfs
  mount: /mnt/btrfs: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error.
         dmesg(1) may have more information after failed mount system call.
  ^^^ RW mount failed as expected ^^^

  # dmesg -t | tail -n5
  loop0: detected capacity change from 0 to 1048576
  BTRFS: device fsid cb5b82f5-0fdd-4d81-9b4b-78533c324afa devid 1 transid 7 /dev/loop0 scanned by mount (1146)
  BTRFS info (device loop0): using crc32c (crc32c-intel) checksum algorithm
  BTRFS info (device loop0): using free space tree
  BTRFS error (device loop0): cannot mount read-write because of unknown compat_ro features (0x403)
  BTRFS error (device loop0): open_ctree failed

  # mount /dev/loop0 -o ro /mnt/btrfs
  # mount -o remount,rw /mnt/btrfs
  ^^^ RW remount succeeded unexpectedly ^^^

[CAUSE]
Currently we use btrfs_check_features() to check compat_ro flags against
our current mount flags.

That function get reused between open_ctree() and btrfs_remount().

But for btrfs_remount(), the super block we passed in still has the old
mount flags, thus btrfs_check_features() still believes we're mounting
read-only.

[FIX]
Replace the existing @sb argument with @is_rw_mount.

As originally we only use @sb to determine if the mount is RW.

Now it's callers' responsibility to determine if the mount is RW, and
since there are only two callers, the check is pretty simple:

- caller in open_ctree()
  Just pass !sb_rdonly().

- caller in btrfs_remount()
  Pass !(*flags & SB_RDONLY), as our check should be against the new
  flags.

Now we can correctly reject the RW remount:

  # mount /dev/loop0 -o ro /mnt/btrfs
  # mount -o remount,rw /mnt/btrfs
  mount: /mnt/btrfs: mount point not mounted or bad option.
         dmesg(1) may have more information after failed mount system call.
  # dmesg -t | tail -n 1
  BTRFS error (device loop0: state M): cannot mount read-write because of unknown compat_ro features (0x403)

Reported-by: Chung-Chiang Cheng <shepjeng@gmail.com>
Fixes: 81d5d61454 ("btrfs: enhance unsupported compat RO flags handling")
CC: stable@vger.kernel.org # 5.15+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2023-01-03 16:22:13 +01:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2007 Oracle. All rights reserved.
*/
#ifndef BTRFS_DISK_IO_H
#define BTRFS_DISK_IO_H
#define BTRFS_SUPER_MIRROR_MAX 3
#define BTRFS_SUPER_MIRROR_SHIFT 12
/*
* Fixed blocksize for all devices, applies to specific ways of reading
* metadata like superblock. Must meet the set_blocksize requirements.
*
* Do not change.
*/
#define BTRFS_BDEV_BLOCKSIZE (4096)
static inline u64 btrfs_sb_offset(int mirror)
{
u64 start = SZ_16K;
if (mirror)
return start << (BTRFS_SUPER_MIRROR_SHIFT * mirror);
return BTRFS_SUPER_INFO_OFFSET;
}
struct btrfs_device;
struct btrfs_fs_devices;
struct btrfs_tree_parent_check;
void btrfs_check_leaked_roots(struct btrfs_fs_info *fs_info);
void btrfs_init_fs_info(struct btrfs_fs_info *fs_info);
int btrfs_verify_level_key(struct extent_buffer *eb, int level,
struct btrfs_key *first_key, u64 parent_transid);
struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
struct btrfs_tree_parent_check *check);
struct extent_buffer *btrfs_find_create_tree_block(
struct btrfs_fs_info *fs_info,
u64 bytenr, u64 owner_root,
int level);
void btrfs_clean_tree_block(struct extent_buffer *buf);
void btrfs_clear_oneshot_options(struct btrfs_fs_info *fs_info);
int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info);
int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
const struct btrfs_super_block *disk_sb);
int __cold open_ctree(struct super_block *sb,
struct btrfs_fs_devices *fs_devices,
char *options);
void __cold close_ctree(struct btrfs_fs_info *fs_info);
int btrfs_validate_super(struct btrfs_fs_info *fs_info,
struct btrfs_super_block *sb, int mirror_num);
int btrfs_check_features(struct btrfs_fs_info *fs_info, bool is_rw_mount);
int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors);
struct btrfs_super_block *btrfs_read_dev_super(struct block_device *bdev);
struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev,
int copy_num, bool drop_cache);
int btrfs_commit_super(struct btrfs_fs_info *fs_info);
struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
struct btrfs_key *key);
int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
struct btrfs_root *root);
void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info);
struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
u64 objectid, bool check_ref);
struct btrfs_root *btrfs_get_new_fs_root(struct btrfs_fs_info *fs_info,
u64 objectid, dev_t anon_dev);
struct btrfs_root *btrfs_get_fs_root_commit_root(struct btrfs_fs_info *fs_info,
struct btrfs_path *path,
u64 objectid);
int btrfs_global_root_insert(struct btrfs_root *root);
void btrfs_global_root_delete(struct btrfs_root *root);
struct btrfs_root *btrfs_global_root(struct btrfs_fs_info *fs_info,
struct btrfs_key *key);
struct btrfs_root *btrfs_csum_root(struct btrfs_fs_info *fs_info, u64 bytenr);
struct btrfs_root *btrfs_extent_root(struct btrfs_fs_info *fs_info, u64 bytenr);
struct btrfs_root *btrfs_block_group_root(struct btrfs_fs_info *fs_info);
void btrfs_free_fs_info(struct btrfs_fs_info *fs_info);
int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info);
void btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info);
void btrfs_btree_balance_dirty_nodelay(struct btrfs_fs_info *fs_info);
void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
struct btrfs_root *root);
int btrfs_validate_metadata_buffer(struct btrfs_bio *bbio,
struct page *page, u64 start, u64 end,
int mirror);
void btrfs_submit_metadata_bio(struct btrfs_inode *inode, struct bio *bio, int mirror_num);
#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
struct btrfs_root *btrfs_alloc_dummy_root(struct btrfs_fs_info *fs_info);
#endif
/*
* This function is used to grab the root, and avoid it is freed when we
* access it. But it doesn't ensure that the tree is not dropped.
*
* If you want to ensure the whole tree is safe, you should use
* fs_info->subvol_srcu
*/
static inline struct btrfs_root *btrfs_grab_root(struct btrfs_root *root)
{
if (!root)
return NULL;
if (refcount_inc_not_zero(&root->refs))
return root;
return NULL;
}
void btrfs_put_root(struct btrfs_root *root);
void btrfs_mark_buffer_dirty(struct extent_buffer *buf);
int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,
int atomic);
int btrfs_read_extent_buffer(struct extent_buffer *buf,
struct btrfs_tree_parent_check *check);
enum btrfs_wq_submit_cmd {
WQ_SUBMIT_METADATA,
WQ_SUBMIT_DATA,
WQ_SUBMIT_DATA_DIO,
};
bool btrfs_wq_submit_bio(struct btrfs_inode *inode, struct bio *bio, int mirror_num,
u64 dio_file_offset, enum btrfs_wq_submit_cmd cmd);
blk_status_t btree_submit_bio_start(struct bio *bio);
int btrfs_alloc_log_tree_node(struct btrfs_trans_handle *trans,
struct btrfs_root *root);
int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info);
int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
struct btrfs_root *root);
void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *trans,
struct btrfs_fs_info *fs_info);
void btrfs_cleanup_one_transaction(struct btrfs_transaction *trans,
struct btrfs_fs_info *fs_info);
struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
u64 objectid);
int btrfs_get_num_tolerated_disk_barrier_failures(u64 flags);
int btrfs_get_free_objectid(struct btrfs_root *root, u64 *objectid);
int btrfs_init_root_free_objectid(struct btrfs_root *root);
#endif
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