On Thu, Dec 16, 2021 at 11:17:09AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Got a report that a repeated crash test of a container host would
> eventually fail with a log recovery error preventing the system from
> mounting the root filesystem. It manifested as a directory leaf node
> corruption on writeback like so:
>
> XFS (loop0): Mounting V5 Filesystem
> XFS (loop0): Starting recovery (logdev: internal)
> XFS (loop0): Metadata corruption detected at xfs_dir3_leaf_check_int+0x99/0xf0, xfs_dir3_leaf1 block 0x12faa158
> XFS (loop0): Unmount and run xfs_repair
> XFS (loop0): First 128 bytes of corrupted metadata buffer:
> 00000000: 00 00 00 00 00 00 00 00 3d f1 00 00 e1 9e d5 8b ........=.......
> 00000010: 00 00 00 00 12 fa a1 58 00 00 00 29 00 00 1b cc .......X...)....
> 00000020: 91 06 78 ff f7 7e 4a 7d 8d 53 86 f2 ac 47 a8 23 ..x..~J}.S...G.#
> 00000030: 00 00 00 00 17 e0 00 80 00 43 00 00 00 00 00 00 .........C......
> 00000040: 00 00 00 2e 00 00 00 08 00 00 17 2e 00 00 00 0a ................
> 00000050: 02 35 79 83 00 00 00 30 04 d3 b4 80 00 00 01 50 .5y....0.......P
> 00000060: 08 40 95 7f 00 00 02 98 08 41 fe b7 00 00 02 d4 .@.......A......
> 00000070: 0d 62 ef a7 00 00 01 f2 14 50 21 41 00 00 00 0c .b.......P!A....
> XFS (loop0): Corruption of in-memory data (0x8) detected at xfs_do_force_shutdown+0x1a/0x20 (fs/xfs/xfs_buf.c:1514). Shutting down.
> XFS (loop0): Please unmount the filesystem and rectify the problem(s)
> XFS (loop0): log mount/recovery failed: error -117
> XFS (loop0): log mount failed
>
> Tracing indicated that we were recovering changes from a transaction
> at LSN 0x29/0x1c16 into a buffer that had an LSN of 0x29/0x1d57.
> That is, log recovery was overwriting a buffer with newer changes on
> disk than was in the transaction. Tracing indicated that we were
> hitting the "recovery immediately" case in
> xfs_buf_log_recovery_lsn(), and hence it was ignoring the LSN in the
^^^^^^^^^^^^^^^^^^^^^^^^^^
xlog_recover_get_buf_lsn()
> buffer.
>
> The code was extracting the LSN correctly, then ignoring it because
> the UUID in the buffer did not match the superblock UUID. The
> problem arises because the UUID check uses the wrong UUID - it
> should be checking the sb_meta_uuid, not sb_uuid. This filesystem
> has sb_uuid != sb_meta_uuid (which is fine), and the buffer has the
> correct matching sb_meta_uuid in it, it's just the code checked it
> against the wrong superblock uuid.
>
> The is no corruption in the filesystem, and failing to recover the
> buffer due to a write verifier failure means the recovery bug did
> not propagate the corruption to disk. Hence there is no corruption
> before or after this bug has manifested, the impact is limited
> simply to an unmountable filesystem....
>
> This was missed back in 2015 during an audit of incorrect sb_uuid
> usage that resulted in commit fcfbe2c4ef42 ("xfs: log recovery needs
> to validate against sb_meta_uuid") that fixed the magic32 buffers to
> validate against sb_meta_uuid instead of sb_uuid. It missed the
> magicda buffers....
>
> Fixes: ce748eaa65f2 ("xfs: create new metadata UUID field and incompat flag")
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
> fs/xfs/xfs_buf_item_recover.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_buf_item_recover.c b/fs/xfs/xfs_buf_item_recover.c
> index 70ca5751b13e..e484251dc9c8 100644
> --- a/fs/xfs/xfs_buf_item_recover.c
> +++ b/fs/xfs/xfs_buf_item_recover.c
> @@ -816,7 +816,7 @@ xlog_recover_get_buf_lsn(
> }
>
> if (lsn != (xfs_lsn_t)-1) {
> - if (!uuid_equal(&mp->m_sb.sb_uuid, uuid))
> + if (!uuid_equal(&mp->m_sb.sb_meta_uuid, uuid))
> goto recover_immediately;
> return lsn;
> }
> --
> 2.33.0
>
>
--
Dave Chinner
david@xxxxxxxxxxxxx
