From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5768AC433B4 for ; Tue, 13 Apr 2021 16:59:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33428613A9 for ; Tue, 13 Apr 2021 16:59:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346991AbhDMRAE (ORCPT ); Tue, 13 Apr 2021 13:00:04 -0400 Received: from mga01.intel.com ([192.55.52.88]:14038 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345936AbhDMRAC (ORCPT ); Tue, 13 Apr 2021 13:00:02 -0400 IronPort-SDR: 5mB13PZ24mG0r+mMVE2i236uN1HMXlk+a/cJ5k3d7msMUcWuwMWM7sScNiI8euwQknGe0PTVGa lIqlGmdddO4Q== X-IronPort-AV: E=McAfee;i="6200,9189,9953"; a="214941197" X-IronPort-AV: E=Sophos;i="5.82,219,1613462400"; d="scan'208";a="214941197" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Apr 2021 09:59:41 -0700 IronPort-SDR: b9JQnHmyNK9H0SxG2ldlD6mtXXg/Cwe1SH7FDueh3LgvnB1ET5V2880Yxkm6i8xK9N1XD7izze ToJ8S6k9gT4w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.82,219,1613462400"; d="scan'208";a="424337626" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.171]) by orsmga008.jf.intel.com with SMTP; 13 Apr 2021 09:59:35 -0700 Received: by stinkbox (sSMTP sendmail emulation); Tue, 13 Apr 2021 19:59:34 +0300 Date: Tue, 13 Apr 2021 19:59:34 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Jisheng Zhang Cc: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter , Chris Wilson , Jon Bloomfield , intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org Subject: Re: [PATCH] drm/i915: Fix "mitigations" parsing if i915 is builtin Message-ID: References: <20210413170240.0d4ffa38@xhacker.debian> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210413170240.0d4ffa38@xhacker.debian> X-Patchwork-Hint: comment Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 13, 2021 at 05:02:40PM +0800, Jisheng Zhang wrote: > I met below error during boot with i915 builtin if pass > "i915.mitigations=off": > [ 0.015589] Booting kernel: `off' invalid for parameter `i915.mitigations' > > The reason is slab subsystem isn't ready at that time, so kstrdup() > returns NULL. Fix this issue by using stack var instead of kstrdup(). > > Fixes: 984cadea032b ("drm/i915: Allow the sysadmin to override security mitigations") > Signed-off-by: Jisheng Zhang > --- > drivers/gpu/drm/i915/i915_mitigations.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_mitigations.c b/drivers/gpu/drm/i915/i915_mitigations.c > index 84f12598d145..7dadf41064e0 100644 > --- a/drivers/gpu/drm/i915/i915_mitigations.c > +++ b/drivers/gpu/drm/i915/i915_mitigations.c > @@ -29,15 +29,13 @@ bool i915_mitigate_clear_residuals(void) > static int mitigations_set(const char *val, const struct kernel_param *kp) > { > unsigned long new = ~0UL; > - char *str, *sep, *tok; > + char str[64], *sep, *tok; > bool first = true; > int err = 0; > > BUILD_BUG_ON(ARRAY_SIZE(names) >= BITS_PER_TYPE(mitigations)); > > - str = kstrdup(val, GFP_KERNEL); > - if (!str) > - return -ENOMEM; > + strncpy(str, val, sizeof(str) - 1); I don't think strncpy() guarantees that the string is properly terminated. Also commit b1b6bed3b503 ("usb: core: fix quirks_param_set() writing to a const pointer") looks broken as well given your findings, and arch/um/drivers/virtio_uml.c seems to suffer from this as well. kernel/params.c itself seems to have some slab_is_available() magic around kmalloc(). I used the following cocci snippet to find these: @find@ identifier O, F; position PS; @@ struct kernel_param_ops O = { ..., .set = F@PS ,... }; @alloc@ identifier ALLOC =~ "^k.*(alloc|dup)"; identifier find.F; position PA; @@ F(...) { <+... ALLOC@PA(...) ...+> } @script:python depends on alloc@ ps << find.PS; pa << alloc.PA; @@ coccilib.report.print_report(ps[0], "struct") coccilib.report.print_report(pa[0], "alloc") That could of course miss a bunch more if they allocate via some other function I didn't consider. -- Ville Syrjälä Intel