diff --git a/fs/jfs/jfs_extent.c b/fs/jfs/jfs_extent.c
--- a/fs/jfs/jfs_extent.c
+++ b/fs/jfs/jfs_extent.c
@@ -326,6 +326,12 @@ extBalloc(struct inode *ip, s64 hint, s64 * nblocks, s64 * blkno)
 	if (bmp->db_maxfreebud == -1)
 		return -ENOSPC;

+	if (bmp->db_maxfreebud < 0 || bmp->db_maxfreebud > 63) {
+		jfs_error(ip->i_sb,
+			  "invalid db_maxfreebud: %d\n", bmp->db_maxfreebud);
+		return -EIO;
+	}
+
 	max = (s64) 1 << bmp->db_maxfreebud;
 	if (*nblocks >= max && *nblocks > nbperpage)
 		nb = nblks = (max > nbperpage) ? max : nbperpage;