From patchwork Tue Oct 27 13:46:07 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 312612 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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, 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 6F257C5517A for ; Tue, 27 Oct 2020 15:27:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B68D206F4 for ; Tue, 27 Oct 2020 15:27:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812461; bh=4RuWZUZzQBdWwwc8UhIj14hBjpAmE/3TkrvqmhbmZYA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=LreQG3Y1sTPgxsTRVyOi4YJO6qWM/8CxViZiGy0ZI8MAzTrSnGqhioU12JI+8pdOz 4ATVja8/FBwuTsvunS+gLIgtnOcY16ryWTK6+Gy6LGWxOXWh9oPPaCwsWjvXqpEhtD ReXTV9Fu8FLjwde/dIF1DM4kzy7KB8UcT+cUmhYE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S368770AbgJ0P1i (ORCPT ); Tue, 27 Oct 2020 11:27:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:37766 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1797318AbgJ0PWu (ORCPT ); Tue, 27 Oct 2020 11:22:50 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0A8B12064B; Tue, 27 Oct 2020 15:22:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603812169; bh=4RuWZUZzQBdWwwc8UhIj14hBjpAmE/3TkrvqmhbmZYA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B+OKIVjeZPTnfC8vG4bcjM4JnskSPAJRjx+3YREjA3vcrzlzjJtst1Z78+D1fc7l+ KX2KpOLMPq/oQtbFEkyQHcqgWHGQDa/j1IylLm0Sb/xYbZcGa6tlJHGGSzintavIub h8kF2FmqJ+5YiE/xq52JdputxxL16jbrPhYtGsL8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Michael Petlan , Jiri Olsa , Ingo Molnar , Peter Zijlstra , Namhyung Kim , Wade Mealing , Sasha Levin Subject: [PATCH 5.9 117/757] perf/core: Fix race in the perf_mmap_close() function Date: Tue, 27 Oct 2020 14:46:07 +0100 Message-Id: <20201027135456.059763721@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135450.497324313@linuxfoundation.org> References: <20201027135450.497324313@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jiri Olsa [ Upstream commit f91072ed1b7283b13ca57fcfbece5a3b92726143 ] There's a possible race in perf_mmap_close() when checking ring buffer's mmap_count refcount value. The problem is that the mmap_count check is not atomic because we call atomic_dec() and atomic_read() separately. perf_mmap_close: ... atomic_dec(&rb->mmap_count); ... if (atomic_read(&rb->mmap_count)) goto out_put; free_uid out_put: ring_buffer_put(rb); /* could be last */ The race can happen when we have two (or more) events sharing same ring buffer and they go through atomic_dec() and then they both see 0 as refcount value later in atomic_read(). Then both will go on and execute code which is meant to be run just once. The code that detaches ring buffer is probably fine to be executed more than once, but the problem is in calling free_uid(), which will later on demonstrate in related crashes and refcount warnings, like: refcount_t: addition on 0; use-after-free. ... RIP: 0010:refcount_warn_saturate+0x6d/0xf ... Call Trace: prepare_creds+0x190/0x1e0 copy_creds+0x35/0x172 copy_process+0x471/0x1a80 _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. Tested-by: Michael Petlan Signed-off-by: Jiri Olsa Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra Acked-by: Namhyung Kim Acked-by: Wade Mealing Fixes: 9bb5d40cd93c ("perf: Fix mmap() accounting hole"); Link: https://lore.kernel.org/r/20200916115311.GE2301783@krava Signed-off-by: Sasha Levin --- kernel/events/core.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index e8bf92202542b..6a1ae6a62d489 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5869,11 +5869,11 @@ static void perf_pmu_output_stop(struct perf_event *event); static void perf_mmap_close(struct vm_area_struct *vma) { struct perf_event *event = vma->vm_file->private_data; - struct perf_buffer *rb = ring_buffer_get(event); struct user_struct *mmap_user = rb->mmap_user; int mmap_locked = rb->mmap_locked; unsigned long size = perf_data_size(rb); + bool detach_rest = false; if (event->pmu->event_unmapped) event->pmu->event_unmapped(event, vma->vm_mm); @@ -5904,7 +5904,8 @@ static void perf_mmap_close(struct vm_area_struct *vma) mutex_unlock(&event->mmap_mutex); } - atomic_dec(&rb->mmap_count); + if (atomic_dec_and_test(&rb->mmap_count)) + detach_rest = true; if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex)) goto out_put; @@ -5913,7 +5914,7 @@ static void perf_mmap_close(struct vm_area_struct *vma) mutex_unlock(&event->mmap_mutex); /* If there's still other mmap()s of this buffer, we're done. */ - if (atomic_read(&rb->mmap_count)) + if (!detach_rest) goto out_put; /*