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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 970C9C3B187 for ; Wed, 12 Feb 2020 23:40:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6EDFB21734 for ; Wed, 12 Feb 2020 23:40:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581550801; bh=7/2xM7iTblevfBuLRF/P0S9IMmXYULbyCxH1xaA5ZyQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=MsdXE1z9xmG/TGerBB7fRe3S5PaLN1VqsJHUPHJGx0Wji6t9VnMA++3LMEmWN79xT jjSmfEsz8Rfc48HBurwdGkJHUyzzEawGW4z210UqKDIpOl2nO2fOmS5EcnbrYjX6c8 jSE6OwdX8Io69CcHH9e4GQOa9IrMZ24HiwZ1//nc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729258AbgBLXkA (ORCPT ); Wed, 12 Feb 2020 18:40:00 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:41320 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729194AbgBLXj6 (ORCPT ); Wed, 12 Feb 2020 18:39:58 -0500 Received: by mail-pg1-f195.google.com with SMTP id 70so2025296pgf.8; Wed, 12 Feb 2020 15:39:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=5FaTihNB0iO6aVJlFQnliVUDjcHxSy/v5NwxGrH8kEI=; b=qEAmDJpjHq1/SDf6Xx5QnzwOEfkQzfaAAuSuJ0sR01YF0yYlVoCLxLOOwV+QGxC1A6 At4V57OeHDRLTUEM5vf09xAy2F5SvJ+57jVcDXKUcwcDgz1ol2m6zScXLJG7OoSu3BWF AsNMxbhzRVlrb5IdNChiSE0Z5R7G10ipo2dnSqTIuSy26l/Yc2Wca1lHimE+eQw7dL3a EFrmpjflcH51ALHlyIJ+xp3f9nuMS3HRz/Nsr/RFsucD8oolwMZuMwHYxV+TxNob5BwB ZmiX8UPIf3vovj+TMAhkkQCfjW1LXhJX+AyqoPTtIQCxX3ctHrDxmuSA3VhkddJQeDAj Gz1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; bh=5FaTihNB0iO6aVJlFQnliVUDjcHxSy/v5NwxGrH8kEI=; b=VdradbErrPzbylSeAPBr+j8TMxU/tKjwcaArh8RfaCpGe0ioaY3ad/mtDW84znNqXk 6QqoiTlSgyVldSMPOBi1aM7u3lwoGouPJVlIN4K5nLJ4ZadoJp8L5qsht8sGDfLNcy9c R9C/xpzNULJUR+IqSUP3G5E10Pk1DYgdBNOR+ZHGlK6tqUnpRof+bS0ounobYq0K9uP5 D8xegNoOxWkB6fvcA0hkwb9u9hN7Hk0HZIIshEVifpY8fFMBppGifxO1YgwIMD8fMQRw smeQ9rnc3+gDu2za/+dDDzITMHw8iLTftqlOB24rQZ3074B1Qm9SWWZquyAqlZYKP0qZ YyYA== X-Gm-Message-State: APjAAAUrRfaThIqwSW1ZcyBjjo33toHBE9DGA7Av/pPYFvFunRKsBRxH rOo23DTXy5Ijv5vtqWLPjFg= X-Google-Smtp-Source: APXvYqwUgswxPMoz82nKSTevATYCfitBRedBrE6cghsT9OKRaDZWTkOVO5apq4PKzc/j/CtkDUG47w== X-Received: by 2002:a63:3c08:: with SMTP id j8mr15003128pga.223.1581550797747; Wed, 12 Feb 2020 15:39:57 -0800 (PST) Received: from bbox-1.mtv.corp.google.com ([2620:15c:211:1:3e01:2939:5992:52da]) by smtp.gmail.com with ESMTPSA id k5sm296664pju.29.2020.02.12.15.39.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Feb 2020 15:39:56 -0800 (PST) From: Minchan Kim To: Andrew Morton Cc: LKML , linux-mm , linux-api@vger.kernel.org, oleksandr@redhat.com, Suren Baghdasaryan , Tim Murray , Daniel Colascione , Sandeep Patil , Sonny Rao , Brian Geffon , Michal Hocko , Johannes Weiner , Shakeel Butt , John Dias , Joel Fernandes , Alexander Duyck , Minchan Kim , Oleg Nesterov Subject: [PATCH v4 3/8] mm: validate mm in do_madvise Date: Wed, 12 Feb 2020 15:39:41 -0800 Message-Id: <20200212233946.246210-4-minchan@kernel.org> X-Mailer: git-send-email 2.25.0.225.g125e21ebc7-goog In-Reply-To: <20200212233946.246210-1-minchan@kernel.org> References: <20200212233946.246210-1-minchan@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg pointed out mm could be nulllified right after mm_access succeeds. This patch validates it before the using. Cc: Oleg Nesterov Signed-off-by: Minchan Kim --- mm/madvise.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 8611f1d39289..bb04c7897eb9 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1073,7 +1073,11 @@ int do_madvise(struct task_struct *task, unsigned long start, int write; size_t len; struct blk_plug plug; - struct mm_struct *mm = task->mm; + struct mm_struct *mm = READ_ONCE(task->mm); + + /* task can exit and nullify its ->mm right after mm_access() */ + if (!mm) + return -ESRCH; start = untagged_addr(start); -- 2.25.0.225.g125e21ebc7-goog