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=-9.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 07F1FC433E2 for ; Thu, 10 Sep 2020 20:55:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A6448214F1 for ; Thu, 10 Sep 2020 20:54:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BhxXHjiT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727801AbgIJUyz (ORCPT ); Thu, 10 Sep 2020 16:54:55 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:49941 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730921AbgIJOuF (ORCPT ); Thu, 10 Sep 2020 10:50:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1599749402; h=from:from:reply-to:subject:subject: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=bvnl+oZNY7fSyrT1rYfr08kEJ6c9MI0yMW+cHdyj6Us=; b=BhxXHjiTwtv9WHCCuq+wUgPt6McGP5ocihLphql9cXHjoyClq/VbdGQ9yAbbBg55pJMfU7 0xAB+L2r7aml4jojc3cuZ6E6vbx6Pzw2FYYSjZj6FZmXsvpuN6yAhRAjoAN9sEm22X3z6x sqe0tixqPMzGgY6iR/06iexiM0mX1bc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-384-1fCbfGeXMlCHyZyhcD0t6g-1; Thu, 10 Sep 2020 10:49:13 -0400 X-MC-Unique: 1fCbfGeXMlCHyZyhcD0t6g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 01AF5425CE; Thu, 10 Sep 2020 14:47:48 +0000 (UTC) Received: from krava (unknown [10.40.192.120]) by smtp.corp.redhat.com (Postfix) with SMTP id D79865C22E; Thu, 10 Sep 2020 14:47:45 +0000 (UTC) Date: Thu, 10 Sep 2020 16:47:44 +0200 From: Jiri Olsa To: Namhyung Kim Cc: Jiri Olsa , Peter Zijlstra , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Alexander Shishkin , Michael Petlan , Wade Mealing Subject: Re: [PATCH] perf: Fix race in perf_mmap_close function Message-ID: <20200910144744.GA1663813@krava> References: <20200910104153.1672460-1-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 10, 2020 at 10:48:02PM +0900, Namhyung Kim wrote: SNIP > > _do_fork+0x83/0x3a0 > > __do_sys_wait4+0x83/0x90 > > __do_sys_clone+0x85/0xa0 > > do_syscall_64+0x5b/0x1e0 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > Using atomic decrease and check instead of separated calls. > > This fixes CVE-2020-14351. > > > > Signed-off-by: Jiri Olsa > > --- > > kernel/events/core.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index 7ed5248f0445..29313cc54d9e 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -5903,8 +5903,6 @@ static void perf_mmap_close(struct vm_area_struct *vma) > > mutex_unlock(&event->mmap_mutex); > > } > > > > - atomic_dec(&rb->mmap_count); > > - > > if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) > > goto out_put; > > But when it takes the goto, rb->mmap_count won't decrement anymore.. event->mmap_count is per event, so if we have have race in here, 2 threads can go through with each event->mmap_count reaching zero jirka