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

Darrick J. Wong
2018-06-05T04:08:21Z

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?

--D

> + if (fa)
> + return fa;
> +
> /* only version 3 or greater inodes are extensively verified here */
> if (dip->di_version < 3)
> return NULL;
> --
> 2.17.0
>
> --
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