On Tue, Jan 16, 2018 at 08:56:48AM +1100, Dave Chinner wrote:
> On Mon, Jan 15, 2018 at 12:04:47PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > In xfs_scrub_dir_rec, we must walk through the directory block entries
> > to arrive at the offset given by the hash structure. If we blindly
> > trust the hash address, we can end up midway into a directory entry and
> > stray outside the block. Found by lastbit fuzzing lents[3].address in
> > xfs/390 with KASAN enabled.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> > ---
> > v2: improve defensive pointer checking (endp theoretically can be null)
> > ---
> > fs/xfs/libxfs/xfs_dir2.h | 1 +
> > fs/xfs/libxfs/xfs_dir2_data.c | 19 +++++++++++++++++++
> > fs/xfs/scrub/dir.c | 30 +++++++++++++++++++++++++++++-
> > 3 files changed, 49 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_dir2.h b/fs/xfs/libxfs/xfs_dir2.h
> > index 1a8f2cf..2c77195 100644
> > --- a/fs/xfs/libxfs/xfs_dir2.h
> > +++ b/fs/xfs/libxfs/xfs_dir2.h
> > @@ -340,5 +340,6 @@ xfs_dir2_leaf_tail_p(struct xfs_da_geometry *geo, struct xfs_dir2_leaf *lp)
> > #define XFS_READDIR_BUFSIZE (32768)
> >
> > unsigned char xfs_dir3_get_dtype(struct xfs_mount *mp, uint8_t filetype);
> > +void *xfs_dir3_data_endp(struct xfs_mount *mp, struct xfs_dir2_data_hdr *hdr);
> >
> > #endif /* __XFS_DIR2_H__ */
> > diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c
> > index 853d9ab..b87db03 100644
> > --- a/fs/xfs/libxfs/xfs_dir2_data.c
> > +++ b/fs/xfs/libxfs/xfs_dir2_data.c
> > @@ -1098,3 +1098,22 @@ xfs_dir2_data_use_free(
> > }
> > *needscanp = needscan;
> > }
> > +
> > +/* Find the end of the entry data in a data/block format dir block. */
> > +void *
> > +xfs_dir3_data_endp(
> > + struct xfs_mount *mp,
> > + struct xfs_dir2_data_hdr *hdr)
> > +{
> > + switch (hdr->magic) {
> > + case cpu_to_be32(XFS_DIR3_BLOCK_MAGIC):
> > + case cpu_to_be32(XFS_DIR2_BLOCK_MAGIC):
> > + return xfs_dir2_block_leaf_p(
> > + xfs_dir2_block_tail_p(mp->m_dir_geo, hdr));
> > + case cpu_to_be32(XFS_DIR3_DATA_MAGIC):
> > + case cpu_to_be32(XFS_DIR2_DATA_MAGIC):
> > + return (char *)hdr + mp->m_dir_geo->blksize;
> > + default:
> > + return NULL;
> > + }
> > +}
>
> Ok, this pattern is used in a few places. e.g.
> xfs_dir2_data_make_free, __xfs_dir3_data_check and
> xfs_dir2_data_freescan_int, so if you're going to add a helper, at
> least convert all the other places there is the same code over to
> use it...
>
> Also, it should be passed a geo struct, not a xfs_mount.
Ok.
--D
> Cheers,
>
> Dave.
>
> --
> Dave Chinner
> david@xxxxxxxxxxxxx
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