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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 C052FC2B9F4 for ; Mon, 14 Jun 2021 10:30:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5964613D0 for ; Mon, 14 Jun 2021 10:30:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233128AbhFNKcp (ORCPT ); Mon, 14 Jun 2021 06:32:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:38272 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232943AbhFNKbn (ORCPT ); Mon, 14 Jun 2021 06:31:43 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 95C22611CA; Mon, 14 Jun 2021 10:29:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623666573; bh=bmft2FcajagDR/odu6MXaQBmZdHh4zPQQTp5ndNVwSQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FAM8qqn3+a9Q5W9P3+E+bjUcaKSBfOT226A3C1Y0d5Z+Y2dmrtSY652BGxAotShFe dCXRbwwW6ZGuGjiEsHrWvvHiRtp/HiQlxxq0G09n/SH+xYuYUjSQdzlIepaUmvZ2Zw iQwD6fWOnFZ68WI+89wYD547fQC36PIJJV0WYyx0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+142c9018f5962db69c7e@syzkaller.appspotmail.com, Marco Elver , "Peter Zijlstra (Intel)" Subject: [PATCH 4.4 28/34] perf: Fix data race between pin_count increment/decrement Date: Mon, 14 Jun 2021 12:27:19 +0200 Message-Id: <20210614102642.487259384@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210614102641.582612289@linuxfoundation.org> References: <20210614102641.582612289@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Marco Elver commit 6c605f8371159432ec61cbb1488dcf7ad24ad19a upstream. KCSAN reports a data race between increment and decrement of pin_count: write to 0xffff888237c2d4e0 of 4 bytes by task 15740 on cpu 1: find_get_context kernel/events/core.c:4617 __do_sys_perf_event_open kernel/events/core.c:12097 [inline] __se_sys_perf_event_open kernel/events/core.c:11933 ... read to 0xffff888237c2d4e0 of 4 bytes by task 15743 on cpu 0: perf_unpin_context kernel/events/core.c:1525 [inline] __do_sys_perf_event_open kernel/events/core.c:12328 [inline] __se_sys_perf_event_open kernel/events/core.c:11933 ... Because neither read-modify-write here is atomic, this can lead to one of the operations being lost, resulting in an inconsistent pin_count. Fix it by adding the missing locking in the CPU-event case. Fixes: fe4b04fa31a6 ("perf: Cure task_oncpu_function_call() races") Reported-by: syzbot+142c9018f5962db69c7e@syzkaller.appspotmail.com Signed-off-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210527104711.2671610-1-elver@google.com Signed-off-by: Greg Kroah-Hartman --- kernel/events/core.c | 2 ++ 1 file changed, 2 insertions(+) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3497,7 +3497,9 @@ find_get_context(struct pmu *pmu, struct cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu); ctx = &cpuctx->ctx; get_ctx(ctx); + raw_spin_lock_irqsave(&ctx->lock, flags); ++ctx->pin_count; + raw_spin_unlock_irqrestore(&ctx->lock, flags); return ctx; }