[PATCH] xfs: add a few more verifier tests

Eric Sandeen
2014-08-19T03:14:17Z

These were exposed by fsfuzzer runs; without them we fail
in various exciting and sometimes convoluted ways when we
encounter disk corruption.

Without the MAXLEVELS tests we tend to walk off the end of
an array in a loop like this:

for (i = 0; i < cur->bc_nlevels; i++) {
if (cur->bc_bufs[i])

Without the dirblklog test we try to allocate more memory
than we could possibly hope for and loop forever:

xfs_dabuf_map()
nfsb = mp->m_dir_geo->fsbcount;
irecs = kmem_zalloc(sizeof(irec) * nfsb, KM_SLEEP...

As for the logbsize check, that's the convoluted one.

If logbsize is specified at mount time, it's sanitized
in xfs_parseargs; in particular it makes sure that it's
not > XLOG_MAX_RECORD_BSIZE.

If not specified at mount time, it comes from the superblock
via sb_logsunit; this is limited to 256k at mkfs time as well;
it's copied into m_logbsize in xfs_finish_flags().

However, if for some reason the on-disk value is corrupt and
too large, nothing catches it. It's a circuitous path, but
that size eventually finds its way to places that make the kernel
very unhappy, leading to oopses in xlog_pack_data() because we
use the size as an index into iclog->ic_data, but the array
is not necessarily that big.

Anyway - bounds checking when we read from disk is a good thing!

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
--

(if this should be separate patches, I can resend if you like)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 4bffffe..a4a9e0e 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2209,6 +2209,10 @@ xfs_agf_verify(
be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp)))
return false;

+ if (!(be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) <= XFS_BTREE_MAXLEVELS &&
+ be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]) <= XFS_BTREE_MAXLEVELS))
+ return false;
+
/*
* during growfs operations, the perag is not fully initialised,
* so we can't use it for any useful checking. growfs ensures we can't
diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index b62771f..ae15060 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -2051,6 +2051,8 @@ xfs_agi_verify(
if (!XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum)))
return false;

+ if (!(be32_to_cpu(agi->agi_level) <= XFS_BTREE_MAXLEVELS))
+ return false;
/*
* during growfs operations, the perag is not fully initialised,
* so we can't use it for any useful checking. growfs ensures we can't
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index ad525a5..8426e5e 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -279,11 +279,13 @@ xfs_mount_validate_sb(
sbp->sb_blocklog < XFS_MIN_BLOCKSIZE_LOG ||
sbp->sb_blocklog > XFS_MAX_BLOCKSIZE_LOG ||
sbp->sb_blocksize != (1 << sbp->sb_blocklog) ||
+ sbp->sb_dirblklog > XFS_MAX_BLOCKSIZE_LOG ||
sbp->sb_inodesize < XFS_DINODE_MIN_SIZE ||
sbp->sb_inodesize > XFS_DINODE_MAX_SIZE ||
sbp->sb_inodelog < XFS_DINODE_MIN_LOG ||
sbp->sb_inodelog > XFS_DINODE_MAX_LOG ||
sbp->sb_inodesize != (1 << sbp->sb_inodelog) ||
+ sbp->sb_logsunit > XLOG_MAX_RECORD_BSIZE ||
sbp->sb_inopblock != howmany(sbp->sb_blocksize,sbp->sb_inodesize) ||
(sbp->sb_blocklog - sbp->sb_inodelog != sbp->sb_inopblog) ||
(sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE) ||