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=-17.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 E2CFFC433FE for ; Wed, 9 Dec 2020 03:22:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A923E224D4 for ; Wed, 9 Dec 2020 03:22:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727195AbgLIDWo (ORCPT ); Tue, 8 Dec 2020 22:22:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46778 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727169AbgLIDWo (ORCPT ); Tue, 8 Dec 2020 22:22:44 -0500 Received: from mail-pf1-x442.google.com (mail-pf1-x442.google.com [IPv6:2607:f8b0:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81212C0613CF for ; Tue, 8 Dec 2020 19:22:04 -0800 (PST) Received: by mail-pf1-x442.google.com with SMTP id 131so92335pfb.9 for ; Tue, 08 Dec 2020 19:22:04 -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:mime-version :content-transfer-encoding; bh=kE2FmGi+NBcEH+7fTQb+PyvwhRcfzZ3tL3pXgj3lp0U=; b=Jy3vrUApDBhHvZJBn57K8e/d2idV4VgedPdQrlFVN8/gHofHQRCSUS+EyLsLWN23kW iUM/EzG1GlZOza3lgi258SgApobYZzbtgkDMrh5X+P6Dtg0wFiRSnm4LY/LvIKrS9Mg2 hSJzzHUTuvM6MNY7peOqsOG3g54lGtivoXq9prMyTHFR9yAaWfdPX8+c7dXRsbuAu2FX qwXAMlXCAy2gKgVbD19TkixdU6BiBA/C8bQdN3Ka6fBa3Pl71bCbtheUT7Uck2dN5ySq I/vz3wsg5ZlvuhpiPYbAsa9l22m4P/cuRzvPt+Ok2EQhqPl32lmspRkLpmv4BNX5rHGI 2Lvg== 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 :mime-version:content-transfer-encoding; bh=kE2FmGi+NBcEH+7fTQb+PyvwhRcfzZ3tL3pXgj3lp0U=; b=fGf7eRNrgstMI7MBoMb35X9ERSRAVdA+MLl+v7/p3iMho/74lPUMQE3ayOD6szGjBA aFVirtMN3Nzm2N2FVtY0LaKNuHd5Zaolzo/8xsTfp4Pgn3OyEViOwekWVOprKnR/y3Sv 5mrRFvQZVgjgMn39A2/TH46PCcVBPF+UTAiz1FEfqzCSvBqM5Z7YkJlfnHU/CKJCk7Ax 97cblul7W9qBu50pMeLtjjGAijGUPsWD3sUd8hhipum2SAdfwTvPk7wgfuXZ1fdT3PO7 DvnOFpQN8F9XCOfoe8TLVOHT1x5mupahmnK0r9So4BesZ09DtVfRTsJGDc3Equp4bvsB aRFg== X-Gm-Message-State: AOAM532VI+G1zvhAY3JeO1szQMCUvCj76RscexmU81B3OXCulv5EJId/ XfYmi1gm7RdRKniXz6Ndo+Q= X-Google-Smtp-Source: ABdhPJzaDkDWI6XXJwPVjvBCKV1E4lYeZm47ZQvRlyCxaueRb7Cz8XT18kQkF76HsVXx+cVLeJA8gw== X-Received: by 2002:a63:471f:: with SMTP id u31mr153252pga.74.1607484123975; Tue, 08 Dec 2020 19:22:03 -0800 (PST) Received: from bbox-1.mtv.corp.google.com ([2620:15c:211:201:7220:84ff:fe09:5e58]) by smtp.gmail.com with ESMTPSA id 10sm216009pjt.35.2020.12.08.19.22.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Dec 2020 19:22:02 -0800 (PST) Sender: Minchan Kim From: Minchan Kim To: akpm@linux-foundation.org, torvalds@linux-foundation.org Cc: LKML , linux-mm , jannh@google.com, mhocko@suse.com, shakeelb@google.com, surenb@google.com, christian@brauner.io, rientjes@google.com, bgeffon@google.com, vbabka@suse.cz, Minchan Kim , security@kernel.org Subject: [PATCH] mm/madvise: remove racy mm ownership check Date: Tue, 8 Dec 2020 19:21:55 -0800 Message-Id: <20201209032155.564991-1-minchan@kernel.org> X-Mailer: git-send-email 2.29.2.576.ga3fc446d84-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jann spotted the security hole due to race of mm ownership check. If the task is sharing the mm_struct but goes through execve() before mm_access(), it could skip process_madvise_behavior_valid check. That makes *any advice hint* to reach into the remote process. This patch removes the mm ownership check. With it, it will lose the ability that local process could give *any* advice hint with vector interface for some reason(e.g., performance). Since there is no concrete example in upstream yet, it would be better to remove the abiliity at this moment and need to review when such new advice comes up. Cc: security@kernel.org Fixes: ecb8ac8b1f14 ("mm/madvise: introduce process_madvise() syscall: an external memory hinting API") Reported-by: Jann Horn Suggested-by: Jann Horn Signed-off-by: Minchan Kim --- mm/madvise.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index a8d8d48a57fe..13f5677b9322 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1204,8 +1204,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, goto put_pid; } - if (task->mm != current->mm && - !process_madvise_behavior_valid(behavior)) { + if (!process_madvise_behavior_valid(behavior)) { ret = -EINVAL; goto release_task; } -- 2.29.2.576.ga3fc446d84-goog