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 A4E2A1A5B92; Sat, 21 Jun 2025 07:49:19 +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=1750492159; cv=none; b=eAvLjPjECO/J6uPdNot+W6t1gvDlEIe1t18kWQZ9r2rdzq2qXTTC4JiuQbkAP2ImePWq6jUIE+20l+EB2dNzMunrqWvcpzm13oybCBNEUMfeGuJ3lsVnhpXzw/RCkA7c/nqLRrZTWmCj1fXm33fTeiYV7hZEvtIr72cM94/VUog= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750492159; c=relaxed/simple; bh=D92eT9Xx7A/mwCmvtvVyVvyYZrjSeDvGxSVWf/q13Vc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZqIja9+KSXIKrwrk17NHSqNMyrAV2x0uiPrKNZbngRB7PVXBhuR0Zoj1ek0yGmliJ6TdTNttYy2YvVmdkaEa26L9S8MsfxJkDlR3omXhRTDaec/JgDQriD4fZczh/DxrLMHpgRHFAcicyuCmKBfDIB5hVdP+6BiHS0HNTO4etdc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b8xiYplK; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b8xiYplK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66C9AC4CEE7; Sat, 21 Jun 2025 07:49:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750492159; bh=D92eT9Xx7A/mwCmvtvVyVvyYZrjSeDvGxSVWf/q13Vc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=b8xiYplKeHRRT583dTNY3TeIFIgxYTewhGYVSF5BzXeVTfy4kV7BqkR87eyo+mGt5 62IxdOEPJ681ntY/t/sDb1BUMSSXoZWfYhf+fXMAcw3LbCl05r9etlDomF54O3mVbZ FVmbBXn2BoT5QKT+2p0Ff/Vwekvc9hmM/TPtRJLxZDGXaXZiWYsv+NK082wt4jsOkd PQB9zGdmzS6R8UdYbbNurKh8laxo2V0NDRRud3QvuK31LVGJf+mypuw6uxFBJT0RQf IYRWePpJdT/SEaUuoDZ3mVsfxDOsrDREdkPQ2A88Xt6W6Gw1f+XLgiwVgt32Pe7wwu ZYntXXfDXoN6g== Date: Sat, 21 Jun 2025 08:49:15 +0100 From: Simon Horman To: Arnd Bergmann Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Arnd Bergmann , Thomas Gleixner , Ingo Molnar , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] myri10ge: avoid uninitialized variable use Message-ID: <20250621074915.GG9190@horms.kernel.org> References: <20250620112633.3505634-1-arnd@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250620112633.3505634-1-arnd@kernel.org> On Fri, Jun 20, 2025 at 01:26:28PM +0200, Arnd Bergmann wrote: > From: Arnd Bergmann > > While compile testing on less common architectures, I noticed that gcc-10 on > s390 finds a bug that all other configurations seem to miss: > > drivers/net/ethernet/myricom/myri10ge/myri10ge.c: In function 'myri10ge_set_multicast_list': > drivers/net/ethernet/myricom/myri10ge/myri10ge.c:391:25: error: 'cmd.data0' is used uninitialized in this function [-Werror=uninitialized] > 391 | buf->data0 = htonl(data->data0); > | ^~ > drivers/net/ethernet/myricom/myri10ge/myri10ge.c:392:25: error: '*((void *)&cmd+4)' is used uninitialized in this function [-Werror=uninitialized] > 392 | buf->data1 = htonl(data->data1); > | ^~ > drivers/net/ethernet/myricom/myri10ge/myri10ge.c: In function 'myri10ge_allocate_rings': > drivers/net/ethernet/myricom/myri10ge/myri10ge.c:392:13: error: 'cmd.data1' is used uninitialized in this function [-Werror=uninitialized] > 392 | buf->data1 = htonl(data->data1); > drivers/net/ethernet/myricom/myri10ge/myri10ge.c:1939:22: note: 'cmd.data1' was declared here > 1939 | struct myri10ge_cmd cmd; > | ^~~ > drivers/net/ethernet/myricom/myri10ge/myri10ge.c:393:13: error: 'cmd.data2' is used uninitialized in this function [-Werror=uninitialized] > 393 | buf->data2 = htonl(data->data2); > drivers/net/ethernet/myricom/myri10ge/myri10ge.c:1939:22: note: 'cmd.data2' was declared here > 1939 | struct myri10ge_cmd cmd; > > It would be nice to understand how to make other compilers catch this as > well, but for the moment I'll just shut up the warning by fixing the > undefined behavior in this driver. > > Signed-off-by: Arnd Bergmann Hi Arnd, That is a lovely mess. Curiously I was not able to reproduce this on s390 with gcc 10.5.0. Perhaps I needed to try harder. Or perhaps the detection is specific to a very narrow set of GCC versions. Regardless I agree with your analysis, but I wonder if the following is also needed so that .data0, 1 and 2 are always initialised when used. diff --git a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c index f9d6ba381361..4743064bc6d4 100644 --- a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c +++ b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c @@ -809,6 +809,7 @@ static int myri10ge_update_mac_address(struct myri10ge_priv *mgp, | (addr[2] << 8) | addr[3]); cmd.data1 = ((addr[4] << 8) | (addr[5])); + cmd.data2 = 0; status = myri10ge_send_cmd(mgp, MXGEFW_SET_MAC_ADDRESS, &cmd, 0); return status; @@ -820,6 +821,9 @@ static int myri10ge_change_pause(struct myri10ge_priv *mgp, int pause) int status, ctl; ctl = pause ? MXGEFW_ENABLE_FLOW_CONTROL : MXGEFW_DISABLE_FLOW_CONTROL; + cmd.data0 = 0, + cmd.data1 = 0, + cmd.data2 = 0, status = myri10ge_send_cmd(mgp, ctl, &cmd, 0); if (status) { ...