diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index cb3cda1390ad..c67ff5df0340 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -2142,6 +2142,12 @@ static void dbAllocBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
 	int size;
 	s8 *leaf;
 
+	agno = blkno >> bmp->db_agl2size;
+	if (agno < 0 || agno >= MAXAG) {
+		jfs_error(bmp->db_ipbmap->i_sb, "%s: agno %d out of range\n", __func__, agno);
+		return;
+	}
+
 	/* pick up a pointer to the leaves of the dmap tree */
 	leaf = dp->tree.stree + LEAFIND;
 
@@ -2289,6 +2295,12 @@ static int dbFreeBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
 	int rc = 0;
 	int size;
 
+	agno = blkno >> bmp->db_agl2size;
+	if (agno < 0 || agno >= MAXAG) {
+		jfs_error(bmp->db_ipbmap->i_sb, "%s: agno %d out of range\n", __func__, agno);
+		return -EIO;
+	}
+
 	/* determine the bit number and word within the dmap of the
 	 * starting block.
 	 */