Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752059AbbGASAG (ORCPT ); Wed, 1 Jul 2015 14:00:06 -0400 Received: from mail-vn0-f46.google.com ([209.85.216.46]:46252 "EHLO mail-vn0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752023AbbGAR76 (ORCPT ); Wed, 1 Jul 2015 13:59:58 -0400 MIME-Version: 1.0 In-Reply-To: References: <1435769495-2025-1-git-send-email-colin.king@canonical.com> <559420DA.3010401@canonical.com> Date: Wed, 1 Jul 2015 18:59:57 +0100 Message-ID: Subject: Re: [PATCH] drm/nouveau: usif_ioctl: ensure returns are initialized From: Emil Velikov To: Ilia Mirkin Cc: Colin Ian King , Ben Skeggs , "dri-devel@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" 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: 2887 Lines: 58 On 1 July 2015 at 18:37, Ilia Mirkin wrote: > On Wed, Jul 1, 2015 at 1:18 PM, Colin Ian King wrote: >> On 01/07/15 18:12, Emil Velikov wrote: >>> On 1 July 2015 at 17:56, Ilia Mirkin wrote: >>>> On Wed, Jul 1, 2015 at 12:51 PM, Colin King wrote: >>>>> From: Colin Ian King >>>>> >>>>> Various usif_ioctl helper functions do not initialize the >>>>> return variable ret and some of the error handling return >>>>> paths just return garbage values that were on the stack (or >>>>> in a register). I believe that in all the cases, the >>>>> initial ret variable should be set to -EINVAL and subsequent >>>>> paths through these helper functions set it appropriately >>>>> otherwise. >>>>> >>>>> Found via static analysis using cppcheck: >>>>> >>>>> [drivers/gpu/drm/nouveau/nouveau_usif.c:138]: >>>>> (error) Uninitialized variable: ret >>>> >>>> It sure would seem that way, wouldn't it? >>>> >>>> #define nvif_unpack(d,vl,vh,m) ({ \ >>>> if ((vl) == 0 || ret == -ENOSYS) { \ >>>> int _size = sizeof(d); \ >>>> if (_size <= size && (d).version >= (vl) && \ >>>> (d).version <= (vh)) { \ >>>> data = (u8 *)data + _size; \ >>>> size = size - _size; \ >>>> ret = ((m) || !size) ? 0 : -E2BIG; \ >>>> } else { \ >>>> ret = -ENOSYS; \ >>>> } \ >>>> } \ >>>> (ret == 0); \ >>>> }) >>>> >>>> So actually it does get initialized, and I guess cppcheck doesn't know >>>> about macros? >> >> Hrm, what about the case when ((vl) == 0 || ret == -ENOSYS) is false, >> where is ret being set in that case? > > Is that actually the case for any of the callsites? gcc would complain > about that... There is one: drm/nouveau/nvkm/engine/disp/nv50.c: if (nvif_unpack(args->v1, 1, 1, true)) Seems like a recent addition though, I don't recall it with back when was introduced. -Emil -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/