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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85698C54ED1 for ; Wed, 28 May 2025 00:03:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A66CE6B007B; Tue, 27 May 2025 20:03:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A3F166B0082; Tue, 27 May 2025 20:03:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 97DD56B0085; Tue, 27 May 2025 20:03:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 7B0776B007B for ; Tue, 27 May 2025 20:03:53 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id E051A1619C3 for ; Wed, 28 May 2025 00:03:52 +0000 (UTC) X-FDA: 83490368304.30.B6F9048 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf04.hostedemail.com (Postfix) with ESMTP id 409564000C for ; Wed, 28 May 2025 00:03:51 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=W2Yrt4de; spf=pass (imf04.hostedemail.com: domain of akpm@linux-foundation.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1748390631; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=krqZ0ke+/FHXi2oOC3aSszcPG61oqn7BP5GXscIVgsw=; b=Q5RD+T/re4aEToj5WRt+X+0aCZ6Lg1FiElx1m7hOBcovepI/W89fzvvrH4p1224wrpZVh8 z/zRkCn1Qr7XeEbWAhFfDnEPrtBIAkBvU+Yu93Mgu7KoqvgNjCmB97eg/L2TJTzVxqGO6V ckPDPObS2z+ZDObmLaC9gaqisE3M+Ko= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=W2Yrt4de; spf=pass (imf04.hostedemail.com: domain of akpm@linux-foundation.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1748390631; a=rsa-sha256; cv=none; b=zw+18TIdKbtRtUiQJBq/DGbcH1mYfZYJ8oED7AE6x8PE3dy1ltvQA6HKZG7Uf9UpBSqsHr I8BuJiMA6Hd7vIPKjTCWUl+Pnlv98tjCLTyIXZikrPwKzyDmUFCjUeXLX+v01Kl/SWoHna dTrYgG5r2DutE1kNQLz0GDWH5QFAoiQ= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 6E9D0A4F23B; Wed, 28 May 2025 00:03:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8862C4CEE9; Wed, 28 May 2025 00:03:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1748390630; bh=i2AzRVeEErFRHIgUttaiRifouTs9OP7lzL2wPaLrh74=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=W2Yrt4debgjw2oNt4JvY5A/dSbTzcsRIOwcx6rC/dm1nPbImHaGiWjC7l2RkBGFJ+ b8YT3sSe1xk3xlACXZBH3OryZhaQl93Qd6mMb6vG4hFFncYbJLBrdnu4UeM1ZdiJY6 oHFuY4anvbcmNywH8sQNK0CCBbCLUJ5IaYmhbukA= Date: Tue, 27 May 2025 17:03:49 -0700 From: Andrew Morton To: Dan Carpenter Cc: oe-kbuild@lists.linux.dev, Yu Zhao , lkp@intel.com, oe-kbuild-all@lists.linux.dev, linux-kernel@vger.kernel.org, Linux Memory Management List Subject: Re: mm/vmscan.c:3504 walk_pte_range() error: uninitialized symbol 'dirty'. Message-Id: <20250527170349.4eb72b40e4c6e2a6c1c6bce6@linux-foundation.org> In-Reply-To: References: <202505152339.fBOfDPsi-lkp@intel.com> <20250523152705.2ecae09e834c66e1327d6748@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 409564000C X-Stat-Signature: h7k7j3nox5wcdsxpdqxia4z3hq39geak X-Rspam-User: X-HE-Tag: 1748390631-2444 X-HE-Meta: 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 Afug+RK2 VY3cQpSVGK3JJe0BGVgwKd75107qXrlUxuJZMG8WOAoqPrkoyhEoPUCgPLbvZQ/UtHES1SXIYMMLQI1IXDmRrUOTDKZLKdLn/yu5osQY5iJSMUHsGEmyKxmVNvDxKwmb71x4ANhXhyyTeEbsgkSCXUlEuKS5WAeOT+k/++OtnBvmdq0ORCm7cCpt1UFowLXHHb4S3sqhCMQ7EOHIFmcbYrPnw5mOmb4e7Ao7E60YcqdKsutjQHrFX2+UamEX5WodwJrxHTXnuQJa6F54FhME6u8vVbLw6X9qQvM7ysVkPNVYAewcBcJiXy/yjeb/aNg92yW+PiYpphl5eKCpQvOGDifQrNyAiTsSOUSdl X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 26 May 2025 15:32:42 +0300 Dan Carpenter wrote: > > Seems to be notabug because last==NULL on the first loop and in this > > case walk_update_folio() will immediately return without touching > > `dirty'. But gee, I can't blame smatch from getting fooled by this. > > That's true, but if walk_update_folio() we not inlined then we would > still consider this a bug. It's undefined behavior in the C standard > to pass uninitialized variables to a function call and also the UBSan > checker will detected it as a read at runtime. > > In production systems the compiler is going to set > "bool dirty = false;" at the start of the function because everyone > runs with CONFIG_CC_HAS_AUTO_VAR_INIT_ZERO=y. Should I send a patch > which does that explicitly? Yes please. And please include some sort of comment to prevent people from optimizing away the fix ;)