xfs: sanitize sb_inopblock in xfs_mount_validate_sb

xfs_mount_validate_sb doesn't check sb_inopblock for sanity (as does its xfs_repair counterpart, FWIW).

If it's out of bounds, we can go off the rails in i.e. xfs_inode_buf_verify(), which uses sb_inopblock as a loop limit when stepping through a metadata buffer.

The problem can be demonstrated easily by corrupting sb_inopblock with xfs_db and trying to mount the result:

# mkfs.xfs -dfile,name=fsfile,size=1g
# xfs_db -x fsfile 
xfs_db> sb 0
xfs_db> write inopblock 512
inopblock = 512
xfs_db> quit

# mount -o loop fsfile  mnt
and we blow up in xfs_inode_buf_verify().

With this patch, we get a (very noisy) corruption error, and fail the mount as we should.

Signed-off-by Eric Sandeen <[email protected]>

---

fs/xfs/xfs_sb.c +0 -0

index b7c9aea..511cce9 100644

xfs_mount_validate_sb doesn't check sb_inopblock for sanity (as does its xfs_repair counterpart, FWIW).

If it's out of bounds, we can go off the rails in i.e. xfs_inode_buf_verify(), which uses sb_inopblock as a loop limit when stepping through a metadata buffer.

The problem can be demonstrated easily by corrupting sb_inopblock with xfs_db and trying to mount the result:

# mkfs.xfs -dfile,name=fsfile,size=1g
# xfs_db -x fsfile 
xfs_db> sb 0
xfs_db> write inopblock 512
inopblock = 512
xfs_db> quit

# mount -o loop fsfile  mnt
and we blow up in xfs_inode_buf_verify().

With this patch, we get a (very noisy) corruption error, and fail the mount as we should.

Signed-off-by Eric Sandeen <[email protected]>

---

fs/xfs/xfs_sb.c +1 -0

index b7c9aea..511cce9 100644
@@ -288,6 +288,7 @@ xfs_mount_validate_sb(
 	    sbp->sb_inodelog < XFS_DINODE_MIN_LOG			||
 	    sbp->sb_inodelog > XFS_DINODE_MAX_LOG			||
 	    sbp->sb_inodesize != (1 << sbp->sb_inodelog)		||
+	    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)	||
 	    (sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE)	||

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