From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965299AbcKNDwx (ORCPT ); Sun, 13 Nov 2016 22:52:53 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45152 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752551AbcKNCEO (ORCPT ); Sun, 13 Nov 2016 21:04:14 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Boris Brezillon" , "Brian Norris" , "Hector Palacios" Date: Mon, 14 Nov 2016 00:14:20 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 092/346] mtd: nand: fix bug writing 1 byte less than page size In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.39-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Hector Palacios commit 144f4c98399e2c0ca60eb414c15a2c68125c18b8 upstream. nand_do_write_ops() determines if it is writing a partial page with the formula: part_pagewr = (column || writelen < (mtd->writesize - 1)) When 'writelen' is exactly 1 byte less than the NAND page size the formula equates to zero, so the code doesn't process it as a partial write, although it should. As a consequence the function remains in the while(1) loop with 'writelen' becoming 0xffffffff and iterating endlessly. The bug may not be easy to reproduce in Linux since user space tools usually force the padding or round-up the write size to a page-size multiple. This was discovered in U-Boot where the issue can be reproduced by writing any size that is 1 byte less than a page-size multiple. For example, on a NAND with 2K page (0x800): => nand erase.part => nand write $loadaddr 7ff [Editor's note: the bug was added in commit 29072b96078f, but moved around in commit 66507c7bc8895 ("mtd: nand: Add support to use nand_base poi databuf as bounce buffer")] Fixes: 29072b96078f ("[MTD] NAND: add subpage write support") Signed-off-by: Hector Palacios Acked-by: Boris Brezillon Signed-off-by: Brian Norris Signed-off-by: Ben Hutchings --- drivers/mtd/nand/nand_base.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -2389,7 +2389,7 @@ static int nand_do_write_ops(struct mtd_ int cached = writelen > bytes && page != blockmask; uint8_t *wbuf = buf; int use_bufpoi; - int part_pagewr = (column || writelen < (mtd->writesize - 1)); + int part_pagewr = (column || writelen < mtd->writesize); if (part_pagewr) use_bufpoi = 1;