diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index a46fa0f3db57..0ca1ad2610df 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -211,6 +211,11 @@ int dbMount(struct inode *ipbmap)
 		goto err_release_metapage;
 	}
 
+	if (((bmp->db_mapsize - 1) >> bmp->db_agl2size) > MAXAG) {
+		err = -EINVAL;
+		goto err_release_metapage;
+	}
+
 	for (i = 0; i < MAXAG; i++)
 		bmp->db_agfree[i] = le64_to_cpu(dbmp_le->dn_agfree[i]);
 	bmp->db_agsize = le64_to_cpu(dbmp_le->dn_agsize);