Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752076AbdHASU3 (ORCPT ); Tue, 1 Aug 2017 14:20:29 -0400 Received: from mail-it0-f48.google.com ([209.85.214.48]:35325 "EHLO mail-it0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751327AbdHASU1 (ORCPT ); Tue, 1 Aug 2017 14:20:27 -0400 MIME-Version: 1.0 In-Reply-To: <20170801120438.1582336-2-arnd@arndb.de> References: <20170726185219.GA57833@beast> <20170801120438.1582336-1-arnd@arndb.de> <20170801120438.1582336-2-arnd@arndb.de> From: Kees Cook Date: Tue, 1 Aug 2017 11:20:26 -0700 X-Google-Sender-Auth: XviAVZK4xTVb1GRTMKNj73V85i4 Message-ID: Subject: Re: [PATCH 2/2] adfs: use 'unsigned' types for memcpy length To: Arnd Bergmann , Stephen Rothwell Cc: Andrew Morton , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1310 Lines: 33 On Tue, Aug 1, 2017 at 5:04 AM, Arnd Bergmann wrote: > After commit 62d1034f53e3 ("fortify: use WARN instead of BUG for now"), we > get a warning in adfs about a possible buffer overflow: > > In function 'memcpy', > inlined from '__adfs_dir_put' at fs/adfs/dir_f.c:318:2, > inlined from 'adfs_f_update' at fs/adfs/dir_f.c:403:2: > include/linux/string.h:305:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter > __read_overflow2(); > ^~~~~~~~~~~~~~~~~~ > > The warning is correct in the sense that a negative 'pos' argument > to the function would have that result. However, this is not a bug, > as we know the position is always positive (in fact, between 5 > and 2007, inclusive) when the function gets called. > > Changing the variable to a unsigned type avoids the problem. I decided > to use 'unsigned int' for the position in the directory and the block > number, as they are both counting things, but use size_t for the > offset and length that get passed into memcpy. This shuts up the > warning. > > Signed-off-by: Arnd Bergmann Acked-by: Kees Cook Thanks for the fix! (Added sfr to Cc since he noticed this too.) -Kees -- Kees Cook Pixel Security