xfs: check for obviously bad level values in the bmbt root

We can't handle a bmbt that's taller than BTREE_MAXLEVELS, and there's
no such thing as a zero-level bmbt (for that we have extents format),
so if we see this, send back an error code.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 5 insertions, 1 deletions

diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index 421341f93bea..25c1e078aef6 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -26,6 +26,7 @@
 #include "xfs_inode.h"
 #include "xfs_trans.h"
 #include "xfs_inode_item.h"
+#include "xfs_btree.h"
 #include "xfs_bmap_btree.h"
 #include "xfs_bmap.h"
 #include "xfs_error.h"
@@ -429,11 +430,13 @@ xfs_iformat_btree(
         /* REFERENCED */
         int                     nrecs;
         int                     size;
+        int                     level;
 
         ifp = XFS_IFORK_PTR(ip, whichfork);
         dfp = (xfs_bmdr_block_t *)XFS_DFORK_PTR(dip, whichfork);
         size = XFS_BMAP_BROOT_SPACE(mp, dfp);
         nrecs = be16_to_cpu(dfp->bb_numrecs);
+        level = be16_to_cpu(dfp->bb_level);
 
         /*
          * blow out if -- fork has less extents than can fit in
@@ -446,7 +449,8 @@ xfs_iformat_btree(
                                         XFS_IFORK_MAXEXT(ip, whichfork) ||
                      XFS_BMDR_SPACE_CALC(nrecs) >
                                         XFS_DFORK_SIZE(dip, mp, whichfork) ||
-                     XFS_IFORK_NEXTENTS(ip, whichfork) > ip->i_d.di_nblocks)) {
+                     XFS_IFORK_NEXTENTS(ip, whichfork) > ip->i_d.di_nblocks) ||
+                     level == 0 || level > XFS_BTREE_MAXLEVELS) {
                 xfs_warn(mp, "corrupt inode %Lu (btree).",
                                         (unsigned long long) ip->i_ino);
                 XFS_CORRUPTION_ERROR("xfs_iformat_btree", XFS_ERRLEVEL_LOW,