Re: [PATCH 2/6] xfs: verify extent size hint is valid in inode verifier

[Eric Sandeen <sandeen@sandeen.net>]

On 6/4/18 11:24 PM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> There are rules for vald extent size hints. We enforce them when
> applications set them, but fuzzers violate those rules and that
> screws us over.
> 
> This results in alignment assertion failures when setting up
> allocations such as this in direct IO:
> 
> XFS: Assertion failed: ap->length, file: fs/xfs/libxfs/xfs_bmap.c, line: 3432
> ....
> Call Trace:
>  xfs_bmap_btalloc+0x415/0x910
>  xfs_bmapi_write+0x71c/0x12e0
>  xfs_iomap_write_direct+0x2a9/0x420
>  xfs_file_iomap_begin+0x4dc/0xa70
>  iomap_apply+0x43/0x100
>  iomap_file_buffered_write+0x62/0x90
>  xfs_file_buffered_aio_write+0xba/0x300
>  __vfs_write+0xd5/0x150
>  vfs_write+0xb6/0x180
>  ksys_write+0x45/0xa0
>  do_syscall_64+0x5a/0x180
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> And from xfs_db:
> 
> core.extsize = 10380288
> 
> Which is not an integer multiple of the block size, and so violates
> Rule #7 for setting extent size hints. Validate extent size hint
> rules in the inode verifier to catch this.

So, I think that if I do:

# mkfs.xfs -f -m crc=0 $TEST_DEV
# ./check xfs/229
# ./check xfs/229

I trip the verifier, because I end up with freed inodes on disk with an
extent size hints but zeroed flags.  

xfs_ifree sets di_flags = 0 but doesn't clear di_extsize; xfs_inode_validate_extsize
says if extsize !=0 and the hint flag is set, it fails

Anyone else see this?

(crc=0 needed because that causes us to actually reread the inode chunks
in xfs_iread vs. /* shortcut IO on inode allocation if possible */

-Eric