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[23.128.96.18]) by mx.google.com with ESMTP id s7si11508826ejc.675.2021.06.14.04.04.30; Mon, 14 Jun 2021 04:04:52 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b=RaOZihZ2; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234544AbhFNLCM (ORCPT + 99 others); Mon, 14 Jun 2021 07:02:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:57326 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234630AbhFNKxi (ORCPT ); Mon, 14 Jun 2021 06:53:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 139B161350; Mon, 14 Jun 2021 10:40:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623667206; bh=On6oMZibtQ5hDoixU34PlfJ/D3LlpjTk1QmYv2rN1Jw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RaOZihZ28RMYjOGFbc9dGzcRPi1xUX90fmkqhU1HK0NlRxIJdsRQoWupIcf1Xu5+N X6KhQ3AMWrgocHS9JPrUvoaS2tM7PZLt+h28Bj5reaXtoFuDNoaUVMgM7ocESzCnHY 4MiLs880rQFoCJwk7KC1R2EtHM5sZT3Cr3o1XPyw= 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 5.4 68/84] perf: Fix data race between pin_count increment/decrement Date: Mon, 14 Jun 2021 12:27:46 +0200 Message-Id: <20210614102648.678909762@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210614102646.341387537@linuxfoundation.org> References: <20210614102646.341387537@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 @@ -4249,7 +4249,9 @@ 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; }