ext4: fix reserved cluster accounting in __es_remove_extent()
authorYe Bin <yebin10@huawei.com>
Thu, 8 Dec 2022 03:34:24 +0000 (11:34 +0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 12 Jan 2023 10:59:01 +0000 (11:59 +0100)
commit820eacbc4e4f66ffb82385aa98eb920f6d61a59c
tree875310605fe1187d9a0e503d3699aa11444f0a84
parent0dcbf4dc3d54aab5990952cfd832042fb300dbe3
ext4: fix reserved cluster accounting in __es_remove_extent()

commit 1da18e38cb97e9521e93d63034521a9649524f64 upstream.

When bigalloc is enabled, reserved cluster accounting for delayed
allocation is handled in extent_status.c.  With a corrupted file
system, it's possible for this accounting to be incorrect,
dsicovered by Syzbot:

EXT4-fs error (device loop0): ext4_validate_block_bitmap:398: comm rep:
bg 0: block 5: invalid block bitmap
EXT4-fs (loop0): Delayed block allocation failed for inode 18 at logical
offset 0 with max blocks 32 with error 28
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs (loop0): Total free blocks count 0
EXT4-fs (loop0): Free/Dirty block details
EXT4-fs (loop0): free_blocks=0
EXT4-fs (loop0): dirty_blocks=32
EXT4-fs (loop0): Block reservation details
EXT4-fs (loop0): i_reserved_data_blocks=2
EXT4-fs (loop0): Inode 18 (00000000845cd634):
i_reserved_data_blocks (1) not cleared!

Above issue happens as follows:
Assume:
sbi->s_cluster_ratio = 16
Step1:
Insert delay block [0, 31] -> ei->i_reserved_data_blocks=2
Step2:
ext4_writepages
  mpage_map_and_submit_extent -> return failed
  mpage_release_unused_pages -> to release [0, 30]
    ext4_es_remove_extent -> remove lblk=0 end=30
      __es_remove_extent -> len1=0 len2=31-30=1
 __es_remove_extent:
 ...
 if (len2 > 0) {
  ...
  if (len1 > 0) {
  ...
  } else {
es->es_lblk = end + 1;
es->es_len = len2;
...
  }
   if (count_reserved)
count_rsvd(inode, lblk, ...);
goto out; -> will return but didn't calculate 'reserved'
 ...
Step3:
ext4_destroy_inode -> trigger "i_reserved_data_blocks (1) not cleared!"

To solve above issue if 'len2>0' call 'get_rsvd()' before goto out.

Reported-by: syzbot+05a0f0ccab4a25626e38@syzkaller.appspotmail.com
Fixes: 8fcc3a580651 ("ext4: rework reserved cluster accounting when invalidating pages")
Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Eric Whitney <enwlinux@gmail.com>
Link: https://lore.kernel.org/r/20221208033426.1832460-2-yebin@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/ext4/extents_status.c