From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753029AbbF2RmA (ORCPT ); Mon, 29 Jun 2015 13:42:00 -0400 Received: from mail-la0-f48.google.com ([209.85.215.48]:33692 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752689AbbF2Rlw (ORCPT ); Mon, 29 Jun 2015 13:41:52 -0400 Date: Mon, 29 Jun 2015 19:41:47 +0200 From: Horacio Mijail =?iso-8859-1?Q?Ant=F3n?= Quiles To: Andrew Morton , Andy Shevchenko , David Howells , Vivek Goyal , linux-kernel@vger.kernel.org, trivial@kernel.org, Joe Perches Subject: [RESEND][PATCH v4] hexdump: fix for non-aligned buffers Message-ID: <20150629174147.GA5757@mija-VirtualBox> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org An hexdump with a buf not aligned to the groupsize causes non-naturally-aligned memory accesses. This was causing a kernel panic on the processor BlackFin BF527, when such an unaligned buffer was fed by the function ubifs_scanned_corruption in fs/ubifs/scan.c . To fix this, if the buffer is not aligned to groupsize in a platform which does not define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, then change the groupsize to 1, so alignment is no longer a problem. This behavior is coherent with the way the function currently deals with inappropriate parameter combinations, which is to fall back to safe "defaults", even if that means changing the output format and the implicit access patterns that could have been expected. Signed-off-by: Horacio Mijail Antón Quiles --- Changes in v4: - Added space before "*/" (per Joe Perches' indication) Changes in v3: - Removed trailing whitespace (per Joe Perches' indication) - Changed git-generated mail header to avoid encoding issues (per Joe Perches' hint) Changes in v2: - Changed from ad-hoc calculation to IS_ALIGNED() for readability (per Joe Perches' indication) - Made the explanation clearer (aligned vs naturally aligned) --- lib/hexdump.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/lib/hexdump.c b/lib/hexdump.c index 7ea0969..a3bd5d5 100644 --- a/lib/hexdump.c +++ b/lib/hexdump.c @@ -124,6 +124,11 @@ int hex_dump_to_buffer(const void *buf, size_t len, int rowsize, int groupsize, if ((len % groupsize) != 0) /* no mixed size output */ groupsize = 1; + /* fall back to 1-byte groups if buf is not aligned to groupsize */ + if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && + !IS_ALIGNED((uintptr_t)buf, groupsize)) + groupsize = 1; + ngroups = len / groupsize; ascii_column = rowsize * 2 + rowsize / groupsize + 1; -- 2.1.4