Re: [PATCH 2/3] xfs: verify extent size hint is valid in inode verifier

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

On Tue, Jun 05, 2018 at 02:24:53PM +1000, Dave Chinner wrote:
> On Mon, Jun 04, 2018 at 09:08:17PM -0700, Darrick J. Wong wrote:
> > On Tue, Jun 05, 2018 at 12:43:12PM +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>
> > > ---
> > >  fs/xfs/libxfs/xfs_inode_buf.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > > 
> > > diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> > > index f5fff1ccb61d..be197c91307b 100644
> > > --- a/fs/xfs/libxfs/xfs_inode_buf.c
> > > +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> > > @@ -385,6 +385,7 @@ xfs_dinode_verify(
> > >  	xfs_ino_t		ino,
> > >  	struct xfs_dinode	*dip)
> > >  {
> > > +	xfs_failaddr_t		fa;
> > >  	uint16_t		mode;
> > >  	uint16_t		flags;
> > >  	uint64_t		flags2;
> > > @@ -501,6 +502,12 @@ xfs_dinode_verify(
> > >  			return __this_address;
> > >  	}
> > >  
> > > +	/* extent size hint validation */
> > > +	fa = xfs_inode_validate_extsize(mp, be32_to_cpu(dip->di_extsize),
> > > +					mode, be32_to_cpu(dip->di_flags));
> > 
> > What if the cowextsize is garbage?  Do we handle that better, or do we
> > blow up there too?
> 
> I haven't checked (it was a v4 image that I was looking at) - are
> the rules the same?

Similar, but not entirely the same.  See xfs_inode_validate_cowextsize. :)

--D

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