--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1385,6 +1385,12 @@ dbAllocAG(struct bmap * bmp, int agno, s64 nblocks, int l2nb, s64 * results)
            (1 << (L2LPERCTL - (bmp->db_agheight << 1))) / bmp->db_agwidth;
        ti = bmp->db_agstart + bmp->db_agwidth * (agno & (agperlev - 1));
 
+       if (ti >= le32_to_cpu(dcp->nleafs)) {
+               jfs_error(bmp->db_ipbmap->i_sb, "Corrupt dmapctl page: ti out of bounds\n");
+               release_metapage(mp);
+               return -EIO;
+       }
+
        /* dmap control page trees fan-out by 4 and a single allocation
         * group may be described by 1 or 2 subtrees within the ag level
         * dmap control page, depending upon the ag size. examine the ag's