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

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Jun 08, 2018 at 11:10:39AM +1000, Dave Chinner wrote:
> On Thu, Jun 07, 2018 at 09:16:31AM -0700, Darrick J. Wong wrote:
> > On Tue, Jun 05, 2018 at 10:10:15AM -0700, Darrick J. Wong wrote:
> > > On Tue, Jun 05, 2018 at 04:24:19PM +1000, 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.
> > > > 
> > > > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > > 
> > > Looks ok modulo my comments in the next patch,
> > > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > FWIW when I applied this to xfsprogs I saw an xfs/033 regression:
> > 
> > Phase 6 - check inode connectivity...
> > reinitializing root directory
> > Metadata corruption detected at 0x5555555c60e0, inode 0x80 dinode
> > 
> > fatal error -- could not iget root inode -- error - 117
> > [Inferior 1 (process 1178) exited with code 01]
> > (gdb) l *(0x5555555c60e0)
> > 0x5555555c60e0 is in libxfs_inode_validate_extsize (xfs_inode_buf.c:729).
> > 
> > We fail the inode verifier while trying to _iget the root inode so that
> > we can reinitialize it; I suspect phase 3 is going to need to check the
> > extent size hints and clear them.
> 
> I'm actually quite happy to see that the continual process of
> hardening the kernel verifiers has got to the point where we are
> starting to expose deficiencies in xfs_repair.
> 
> Can I wait for the xfsprogs libxfs-4.18-sync branch to pick up these
> verifier changes before looking at what repair needs to do to avoid
> it? I don't want to do a forced context switch to
> debugging/enhancing userspace code right at this moment....

That's ultimately up to Eric, but since fixing it is nontrivial surgery
on xfs_repair (and the verifier update patch doesn't itself break the
build) I'd be fine with fixing it after the 4.18 sync goes in.

--D

> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com
> --
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