From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8CA4E1F7580; Mon, 23 Jun 2025 22:14:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750716889; cv=none; b=ELvd7CDXbgH5Zqz4rbavO1ubv+TFmc6ssLnZn/RnOySfoECcXUQ+xGIUTTxiRqph8ti3ujNp5BgCwuUv3PtoFoebzvWx/rqcZNXMTjKjGtHeqs7T00hjWigemO33kUSsdkWMLgqHskFMocoWux1rBtX3DS2pLmrLv+RUuZFsqeY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750716889; c=relaxed/simple; bh=1z+8MjPfUVE8G3OvRZYvmtoN52VZ0brFrAtjp6asl6I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=uJQYzu6h7jm0pkJkQmjU5nKicjK9QUaJ/zuEw8UCZexV4K/viWRDy1RFQArYm7MTP6Yk8Ll1RTKehRG+uu6I+W+YZp312ZpiH6+gQL7u3XNb0fEkok/j7Xsk4YeWZERPOmcUv3QCCrCD0h+5id+HnzFEQRqefx7kSpzrQp0THsA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=w1JnCroq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="w1JnCroq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD74EC4CEEA; Mon, 23 Jun 2025 22:14:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750716889; bh=1z+8MjPfUVE8G3OvRZYvmtoN52VZ0brFrAtjp6asl6I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w1JnCroqnNpnhe6YecD1k5c0o6u89Yhh5asTJRX7i8bo0gqWDSeDKWflptaHgQT4C NhGIwUsdMCyV4TGSwnFVLvBiDbiMRPsJ6Ess3lf7V7UvHzCd2lXV0gTqO2UL9tJ73x 3MkTwJ4VhGcKBPoVHEb6zfxhBPrU7OPsHuwJX7mw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, kernel test robot , Timur Tabi , Jacob Keller , Danilo Krummrich , Sasha Levin Subject: [PATCH 5.15 367/411] drm/nouveau/bl: increase buffer size to avoid truncate warning Date: Mon, 23 Jun 2025 15:08:31 +0200 Message-ID: <20250623130642.880943915@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130632.993849527@linuxfoundation.org> References: <20250623130632.993849527@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jacob Keller [ Upstream commit 61b2b3737499f1fb361a54a16828db24a8345e85 ] The nouveau_get_backlight_name() function generates a unique name for the backlight interface, appending an id from 1 to 99 for all backlight devices after the first. GCC 15 (and likely other compilers) produce the following -Wformat-truncation warning: nouveau_backlight.c: In function ‘nouveau_backlight_init’: nouveau_backlight.c:56:69: error: ‘%d’ directive output may be truncated writing between 1 and 10 bytes into a region of size 3 [-Werror=format-truncation=] 56 | snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", nb); | ^~ In function ‘nouveau_get_backlight_name’, inlined from ‘nouveau_backlight_init’ at nouveau_backlight.c:351:7: nouveau_backlight.c:56:56: note: directive argument in the range [1, 2147483647] 56 | snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", nb); | ^~~~~~~~~~~~~~~~ nouveau_backlight.c:56:17: note: ‘snprintf’ output between 14 and 23 bytes into a destination of size 15 56 | snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", nb); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The warning started appearing after commit ab244be47a8f ("drm/nouveau: Fix a potential theorical leak in nouveau_get_backlight_name()") This fix for the ida usage removed the explicit value check for ids larger than 99. The compiler is unable to intuit that the ida_alloc_max() limits the returned value range between 0 and 99. Because the compiler can no longer infer that the number ranges from 0 to 99, it thinks that it could use as many as 11 digits (10 + the potential - sign for negative numbers). The warning has gone unfixed for some time, with at least one kernel test robot report. The code breaks W=1 builds, which is especially frustrating with the introduction of CONFIG_WERROR. The string is stored temporarily on the stack and then copied into the device name. Its not a big deal to use 11 more bytes of stack rounding out to an even 24 bytes. Increase BL_NAME_SIZE to 24 to avoid the truncation warning. This fixes the W=1 builds that include this driver. Compile tested only. Fixes: ab244be47a8f ("drm/nouveau: Fix a potential theorical leak in nouveau_get_backlight_name()") Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202312050324.0kv4PnfZ-lkp@intel.com/ Suggested-by: Timur Tabi Signed-off-by: Jacob Keller Link: https://lore.kernel.org/r/20250610-jk-nouveua-drm-bl-snprintf-fix-v2-1-7fdd4b84b48e@intel.com Signed-off-by: Danilo Krummrich Signed-off-by: Sasha Levin --- drivers/gpu/drm/nouveau/nouveau_backlight.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c index aa8ed08fe9a7c..596a16b8b2de9 100644 --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c @@ -40,7 +40,7 @@ #include "nouveau_connector.h" static struct ida bl_ida; -#define BL_NAME_SIZE 15 // 12 for name + 2 for digits + 1 for '\0' +#define BL_NAME_SIZE 24 // 12 for name + 11 for digits + 1 for '\0' static bool nouveau_get_backlight_name(char backlight_name[BL_NAME_SIZE], -- 2.39.5