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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FB95C4321E for ; Wed, 2 Nov 2022 15:44:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230450AbiKBPnv (ORCPT ); Wed, 2 Nov 2022 11:43:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55790 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230489AbiKBPna (ORCPT ); Wed, 2 Nov 2022 11:43:30 -0400 Received: from mail-pj1-x102f.google.com (mail-pj1-x102f.google.com [IPv6:2607:f8b0:4864:20::102f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7329328700 for ; Wed, 2 Nov 2022 08:43:29 -0700 (PDT) Received: by mail-pj1-x102f.google.com with SMTP id b11so16618076pjp.2 for ; Wed, 02 Nov 2022 08:43:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=pWzb2SKkWTuON7pNcNwFRnwOMg1HNM3x+PlBBYRnE78=; b=b1IH6B/wne44OiQXZ9i7FSHJfVW3zIn74ViSqHYAsPnDbPDFo4b0mp4Ea/23Y8yiZp 4Na6VVGOm+h4UD3nlKM9Rl3pFiFLTzf9UB+jUhfO+J4ZNn+X8eC78BvcBr769QMsJqUU WTfGJ4gwtPde3j8W3mqjzgHAHbhf+xT06ghwE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=pWzb2SKkWTuON7pNcNwFRnwOMg1HNM3x+PlBBYRnE78=; b=BX1QXP1m7lr62A8c3QS9QyRQbWbiyTIAFvGI/Wcu5fvP4ZoZywNjfnlEuAj13Vu0rF AisQ0BTmhyX0rBjVkUc75Y6tO7DQXagUmNmaMwAl87GCQIR+QrzIy/I3qBT7Ua+z4VtD dh7q+Xe6V4TQG2loNTIAEmMPpAcai7wZeu88eLR+il1hwaxc7Sp27FxFoTooFBPdYnLo kqnbuVfGG8+oZgahlNxzO0lNGlKP6MUBePDzvtJ3XCbbkDRm3FoBPNaAr+GjRPVgHXmE HWj4JPhch7hYqVTN1zkl6TAMOyDIkUzLDvG4Q3kwGwBxuS4IJCyML46A/ak5NgQmAhyv GjfQ== X-Gm-Message-State: ACrzQf0tqeXedHZkz4Zy7UUDGf64tN9QOT7nQYFSd+irUOQnM+b+rjfo lawmGSeXTnogMSVJ21HSuPIV4A== X-Google-Smtp-Source: AMsMyM7PDeQil3IUTDK8DEQhhfPtLai6Y8bKaPW2tqDAKdyYKrgbMX/ec7FMD6Z/EWccGgv35ijpyA== X-Received: by 2002:a17:903:32cf:b0:187:4b3a:15fd with SMTP id i15-20020a17090332cf00b001874b3a15fdmr2922849plr.99.1667403808948; Wed, 02 Nov 2022 08:43:28 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id w10-20020aa79a0a000000b0056c681af185sm8605569pfj.87.2022.11.02.08.43.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Nov 2022 08:43:28 -0700 (PDT) Date: Wed, 2 Nov 2022 08:43:27 -0700 From: Kees Cook To: Nathan Chancellor Cc: Stefan Agner , Alison Wang , dri-devel@lists.freedesktop.org, Nick Desaulniers , Tom Rix , Sami Tolvanen , llvm@lists.linux.dev, linux-kernel@vger.kernel.org, patches@lists.linux.dev Subject: Re: [PATCH] drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid() Message-ID: <202211020843.A19F75B@keescook> References: <20221102154215.78059-1-nathan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221102154215.78059-1-nathan@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 02, 2022 at 08:42:15AM -0700, Nathan Chancellor wrote: > With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), > indirect call targets are validated against the expected function > pointer prototype to make sure the call target is valid to help mitigate > ROP attacks. If they are not identical, there is a failure at run time, > which manifests as either a kernel panic or thread getting killed. A > proposed warning in clang aims to catch these at compile time, which > reveals: > > drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c:74:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] > .mode_valid = fsl_dcu_drm_connector_mode_valid, > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 1 error generated. > > ->mode_valid() in 'struct drm_connector_helper_funcs' expects a return > type of 'enum drm_mode_status', not 'int'. Adjust the return type of > fsl_dcu_drm_connector_mode_valid() to match the prototype's to resolve > the warning and CFI failure. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1750 > Reported-by: Sami Tolvanen > Signed-off-by: Nathan Chancellor Reviewed-by: Kees Cook -- Kees Cook