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 B38BCC433EF for ; Tue, 15 Feb 2022 19:36:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1E1796B007B; Tue, 15 Feb 2022 14:36:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1901D6B007D; Tue, 15 Feb 2022 14:36:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F27F06B007E; Tue, 15 Feb 2022 14:36:11 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0162.hostedemail.com [216.40.44.162]) by kanga.kvack.org (Postfix) with ESMTP id CFDE86B007D for ; Tue, 15 Feb 2022 14:36:11 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 9394895AF9 for ; Tue, 15 Feb 2022 19:36:11 +0000 (UTC) X-FDA: 79146020142.09.1EF5824 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf11.hostedemail.com (Postfix) with ESMTP id 051DB40005 for ; Tue, 15 Feb 2022 19:36:10 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 921C51F382; Tue, 15 Feb 2022 19:36:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1644953769; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ii5TNPWsUIAw9A7FnVbIdGfffp+xa+Xc1AZj2a+jkto=; b=ii/Z6CGN1NybTstlvc1PJeSPlw7jeLLEf4yJ0N3iydUQMZ4W73O1hjmYbZOJJ3kmcxketp WxSLGwC0YW0ZrK1j/Bh/BmTt8TX9AyDJHjOWSvrUTqnvov20ZM+kUynCs0Vk+sHIPeS0eD MHOIc0TRYJnf1ZAf3AYyfDnSTGsmQtU= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 62467A3B83; Tue, 15 Feb 2022 19:36:09 +0000 (UTC) Date: Tue, 15 Feb 2022 20:36:05 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: Yang Shi , syzbot , Andrew Morton , Christian Brauner , Linux Kernel Mailing List , Linux MM , syzkaller-bugs Subject: Re: [syzbot] KASAN: use-after-free Read in __oom_reap_task_mm Message-ID: References: <00000000000072ef2c05d7f81950@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 051DB40005 X-Rspam-User: Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b="ii/Z6CGN"; spf=pass (imf11.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Stat-Signature: nfau6o4966mwid1s1g1fojoa58d6rdog X-HE-Tag: 1644953770-455137 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: On Tue 15-02-22 10:10:53, Suren Baghdasaryan wrote: > On Tue, Feb 15, 2022 at 9:53 AM Yang Shi wrote: [...] > > Isn't the below race possible? > > > > CPU A CPU B > > exiting: > > mmap_write_lock > > remove_vma() > > mmap_write_unlock > > process_mrelease: > > mmap_read_lock > > __oom_reap_task_mm > > mmap_read_unlock > > > > Sure, that sequence (would not call it a race) is possible but in this > case __oom_reap_task_mm will find no vmas in the mm because exit_mmap > freed and removed all of them. I didn't really have chance to have a closer look but I do not see exit_mmap doing mm->mmap = NULL so the pointer can be a freed vma unless I am missing something. I thought we've had it in your patches? Has this got lost somewhere in the process? -- Michal Hocko SUSE Labs