xfs: fix btree scrub checking with regards to root-in-inode

In xchk_btree_check_owner, we can be passed a null buffer pointer.  This
should only happen for the root of a root-in-inode btree type, but we
should program defensively in case the btree cursor state ever gets
screwed up and we get a null buffer anyway.

Coverity-id: 1438713
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/fs/xfs/scrub/btree.c b/fs/xfs/scrub/btree.c
index 6f94d1f7322d..117910db51b8 100644
--- a/fs/xfs/scrub/btree.c
+++ b/fs/xfs/scrub/btree.c
@@ -415,8 +415,17 @@ xchk_btree_check_owner(
         struct xfs_btree_cur    *cur = bs->cur;
         struct check_owner      *co;
 
-        if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) && bp == NULL)
+        /*
+         * In theory, xfs_btree_get_block should only give us a null buffer
+         * pointer for the root of a root-in-inode btree type, but we need
+         * to check defensively here in case the cursor state is also screwed
+         * up.
+         */
+        if (bp == NULL) {
+                if (!(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE))
+                        xchk_btree_set_corrupt(bs->sc, bs->cur, level);
                 return 0;
+        }
 
         /*
          * We want to cross-reference each btree block with the bnobt