diff --git a/drivers/mtd/chips/gen_probe.c b/drivers/mtd/chips/gen_probe.c
index 9b252d2e4a70..b2d30525c04c 100644
--- a/drivers/mtd/chips/gen_probe.c
+++ b/drivers/mtd/chips/gen_probe.c
@@ -37,8 +37,15 @@ struct mtd_info *mtd_do_chip_probe(struct map_info *map, struct chip_probe *cp)
 	if (!mtd)
 		mtd = check_cmd_set(map, 0); /* Then the secondary */
 
-	if (mtd)
+	if (mtd) {
+		if (mtd->size > map->size) {
+			printk(KERN_WARNING "Reducing visibility of %lKiB chip to %lKiB\n",
+			       (unsigned long)mtd->size >> 10, 
+			       (unsigned long)map->size >> 10);
+			mtd->size = map->size;
+		}
 		return mtd;
+	}
 
 	printk(KERN_WARNING"gen_probe: No supported Vendor Command Set found\n");
 
@@ -100,7 +107,12 @@ static struct cfi_private *genprobe_ident_chips(struct map_info *map, struct chi
 	 * Align bitmap storage size to full byte.
 	 */
 	max_chips = map->size >> cfi.chipshift;
-	mapsize = (max_chips / 8) + ((max_chips % 8) ? 1 : 0);
+	if (!max_chips) {
+		printk(KERN_WARNING "NOR chip too large to fit in mapping. Attempting to cope...\n");
+		max_chips = 1;
+	}
+
+	mapsize = (max_chips + BITS_PER_LONG-1) / BITS_PER_LONG;
 	chip_map = kmalloc(mapsize, GFP_KERNEL);
 	if (!chip_map) {
 		printk(KERN_WARNING "%s: kmalloc failed for CFI chip map\n", map->name);