mtd: cfi_cmdset_0002: fix SEGV unlocking multiple chips

cfi_ppb_unlock() tries to relock all sectors that were locked before
unlocking the whole chip.
This locking used the chip start address + the FULL offset from the
first flash chip, thereby forming an illegal address. Fix that by using
the chip offset(adr).

Fixes: 1648eaaa ("mtd: cfi_cmdset_0002: Support Persistent Protection Bits (PPB) locking")
Cc: stable@vger.kernel.org
Signed-off-by: Joakim Tjernlund <joakim.tjernlund@infinera.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>

drivers/mtd/chips/cfi_cmdset_0002.c

@@ -2526,7 +2526,7 @@ static int cfi_atmel_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 
 struct ppb_lock {
 	struct flchip *chip;
-	loff_t offset;
+	unsigned long adr;
 	int locked;
 };
 
@@ -2662,7 +2662,7 @@ static int __maybe_unused cfi_ppb_unlock(struct mtd_info *mtd, loff_t ofs,
 		 */
 		if ((adr < ofs) || (adr >= (ofs + len))) {
 			sect[sectors].chip = &cfi->chips[chipnum];
-			sect[sectors].offset = offset;
+			sect[sectors].adr = adr;
 			sect[sectors].locked = do_ppb_xxlock(
 				map, &cfi->chips[chipnum], adr, 0,
 				DO_XXLOCK_ONEBLOCK_GETLOCK);
@@ -2706,7 +2706,7 @@ static int __maybe_unused cfi_ppb_unlock(struct mtd_info *mtd, loff_t ofs,
 	 */
 	for (i = 0; i < sectors; i++) {
 		if (sect[i].locked)
-			do_ppb_xxlock(map, sect[i].chip, sect[i].offset, 0,
+			do_ppb_xxlock(map, sect[i].chip, sect[i].adr, 0,
 				      DO_XXLOCK_ONEBLOCK_LOCK);
 	}