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=-11.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS 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 48325C43219 for ; Fri, 3 May 2019 04:39:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 112882081C for ; Fri, 3 May 2019 04:39:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="WbnuGeem"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="fpIR+sx5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726450AbfECEi7 (ORCPT ); Fri, 3 May 2019 00:38:59 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:38780 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726121AbfECEi7 (ORCPT ); Fri, 3 May 2019 00:38:59 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 8FD2961132; Fri, 3 May 2019 04:38:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1556858337; bh=tmO9bZ8OSVF3w2WCn5bCHHR5VcAERihrVuWPn4eTVVo=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=WbnuGeem6wmks0G9pvkliRJ6bjIvrLEVb6rrx++NvPHTdORn3mOwTDs6+pFTzinpB h7Kf6R/cDEEoHkPiwIUZ5WBrAPbCVfcRWKaVQft497o7Q7dKMqfRukBXM/YWKzBKwy lCyBYfXos0w7Fk8v81YA1Frrw92+fKX/lOmk24Bc= Received: from potku.adurom.net (88-114-240-156.elisa-laajakaista.fi [88.114.240.156]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: kvalo@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id 0C86761132; Fri, 3 May 2019 04:38:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1556858336; bh=tmO9bZ8OSVF3w2WCn5bCHHR5VcAERihrVuWPn4eTVVo=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=fpIR+sx5CPmg8HXT9vrjKMg1KHUbBWFs1aO5cxUOWDpbKGz2qI2tfGlh57TuLckqx gjobOfW5e64o+zFQ489u4LtJX981TYPVJPcfR85Qv6SHq29+HXvxjfEihIZXNqnT9T R7L0A2poNp4dT2nbjSvNiW9qvzgHAoetI7ndp0Gk= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 0C86761132 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=kvalo@codeaurora.org From: Kalle Valo To: Nick Desaulniers Cc: Nathan Chancellor , Amitkumar Karwar , Siva Rebbagondla , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, LKML , clang-built-linux Subject: Re: [PATCH] rsi: Properly initialize data in rsi_sdio_ta_reset References: <20190502151548.11143-1-natechancellor@gmail.com> Date: Fri, 03 May 2019 07:38:52 +0300 In-Reply-To: (Nick Desaulniers's message of "Thu, 2 May 2019 11:18:01 -0700") Message-ID: <87h8ackv8j.fsf@kamboji.qca.qualcomm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nick Desaulniers writes: > On Thu, May 2, 2019 at 8:16 AM Nathan Chancellor > wrote: >> >> When building with -Wuninitialized, Clang warns: >> >> drivers/net/wireless/rsi/rsi_91x_sdio.c:940:43: warning: variable 'data' >> is uninitialized when used here [-Wuninitialized] >> put_unaligned_le32(TA_HOLD_THREAD_VALUE, data); >> ^~~~ >> drivers/net/wireless/rsi/rsi_91x_sdio.c:930:10: note: initialize the >> variable 'data' to silence this warning >> u8 *data; >> ^ >> = NULL >> 1 warning generated. >> >> Using Clang's suggestion of initializing data to NULL wouldn't work out >> because data will be dereferenced by put_unaligned_le32. Use kzalloc to >> properly initialize data, which matches a couple of other places in this >> driver. >> >> Fixes: e5a1ecc97e5f ("rsi: add firmware loading for 9116 device") >> Link: https://github.com/ClangBuiltLinux/linux/issues/464 >> Signed-off-by: Nathan Chancellor >> --- >> drivers/net/wireless/rsi/rsi_91x_sdio.c | 21 ++++++++++++++------- >> 1 file changed, 14 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/net/wireless/rsi/rsi_91x_sdio.c b/drivers/net/wireless/rsi/rsi_91x_sdio.c >> index f9c67ed473d1..b35728564c7b 100644 >> --- a/drivers/net/wireless/rsi/rsi_91x_sdio.c >> +++ b/drivers/net/wireless/rsi/rsi_91x_sdio.c >> @@ -929,11 +929,15 @@ static int rsi_sdio_ta_reset(struct rsi_hw *adapter) >> u32 addr; >> u8 *data; >> >> + data = kzalloc(sizeof(u32), GFP_KERNEL); > > Something fishy is going on here. We allocate 4 B but declare data as > a u8* (pointer to individual bytes)? In general, dynamically > allocating that few bytes is a code smell; either you meant to just > use the stack, or this memory's lifetime extends past the lifetime of > this stackframe, at which point you probably just meant to stack > allocate space in a higher parent frame and pass this preallocated > memory down to the child frame to get filled in. > > Reading through this code, I don't think that the memory is meant to > outlive the stack frame. Is there a reason why we can't just declare > data as: > > u8 data [4]; > > then use ARRAY_SIZE(data) or RSI_9116_REG_SIZE in rsi_reset_chip(), > getting rid of the kzalloc/kfree? I haven't checked the details but AFAIK stack variables are not supposed to be used with DMA. So in that case I think it's ok alloc four bytes, unless the DMA rules have changed of course. But I didn't check if rsi is using DMA here, just a general comment. -- Kalle Valo