From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C33A77461 for ; Wed, 2 Nov 2022 19:22:12 +0000 (UTC) Received: by mail-pf1-f181.google.com with SMTP id d10so17278748pfh.6 for ; Wed, 02 Nov 2022 12:22:12 -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=4EDI3vYbHaaiAQeZuuGzJ5Pv1WpOR32gAtsS0QDWLuw=; b=cf2nTr5YnckoTzWzbGWmtwmcSXrd8AamU45cN4BkmLr5woysN2W1kdbIKrPwII4PVI ce8I7YTY4uSDnL6ZPBTz94gxiF8GCs7pA974P296j4z8qCIMA1+np81HnE/zTRa6yv+M k3Z8gi82o4u4QsaXVn9ASZodldSA4+ubXIZL0= 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=4EDI3vYbHaaiAQeZuuGzJ5Pv1WpOR32gAtsS0QDWLuw=; b=LnOaSxYChws2YihKA0nmI7yEQaD1yi+jc9TKcksESHfIWB4IzohViRl0Ade8DmoEU5 var/0EpCPloinnQfKljNSRauRv/47XzZpNjc05SeX+z5Sa0Zj334CVpM9OAEjoFN1LEs u12y8LDYPgu2xxPGmJHv8uPQYuuuydl91b0KUm+b57oaLl8b3mkIz3iI5AuKvnGISCub q8TlYVuNhJpljA1Dhmbg6TD972M0QMacMLw86FBY7trszfr2uROzZ5QnLgGz1nkIFIxL jiT0YeznqCO+85je0uwyHJvV+ismInNTWr3xcHw/tUa0NvvHKNOHMvTHp+FZl7XLAzo+ /v6A== X-Gm-Message-State: ACrzQf0JYrIiEPvg5vt7W6k7rawK1SgUXHZUgjXF64p6cFPRUsVLOGeE dcudPO4+eoqbOWF7rcFpUu3Jbw== X-Google-Smtp-Source: AMsMyM6VtLTeGYSXsL6Ro3gC8gkszOK2+Cjl0KViNXychOWaLiDIqn26ITH/JYsmSRn3aX4X3qwIeQ== X-Received: by 2002:a05:6a00:1391:b0:56d:2b6f:57b3 with SMTP id t17-20020a056a00139100b0056d2b6f57b3mr23293181pfg.56.1667416932256; Wed, 02 Nov 2022 12:22:12 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id 85-20020a621658000000b005609d3d3008sm9054723pfw.171.2022.11.02.12.22.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Nov 2022 12:22:11 -0700 (PDT) Date: Wed, 2 Nov 2022 12:22:11 -0700 From: Kees Cook To: Nathan Chancellor Cc: Chun-Kuang Hu , Philipp Zabel , dri-devel@lists.freedesktop.org, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Nick Desaulniers , Tom Rix , Sami Tolvanen , llvm@lists.linux.dev, linux-kernel@vger.kernel.org, patches@lists.linux.dev Subject: Re: [PATCH] drm/mediatek: Fix return type of mtk_hdmi_bridge_mode_valid() Message-ID: <202211021222.1E8A8BCB43@keescook> References: <20221102154712.540548-1-nathan@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221102154712.540548-1-nathan@kernel.org> On Wed, Nov 02, 2022 at 08:47:12AM -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/mediatek/mtk_hdmi.c:1407:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' with an expression of type 'int (struct drm_bridge *, const struct drm_display_info *, const struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] > .mode_valid = mtk_hdmi_bridge_mode_valid, > ^~~~~~~~~~~~~~~~~~~~~~~~~~ > 1 error generated. > > ->mode_valid() in 'struct drm_bridge_funcs' expects a return type of > 'enum drm_mode_status', not 'int'. Adjust the return type of > mtk_hdmi_bridge_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