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[23.128.96.18]) by mx.google.com with ESMTP id l4si2952716edi.316.2020.06.18.14.26.20; Thu, 18 Jun 2020 14:26:42 -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; 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=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730958AbgFROs7 (ORCPT + 99 others); Thu, 18 Jun 2020 10:48:59 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:37707 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726927AbgFROs6 (ORCPT ); Thu, 18 Jun 2020 10:48:58 -0400 Received: by mail-wm1-f67.google.com with SMTP id y20so5967608wmi.2 for ; Thu, 18 Jun 2020 07:48:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=+xS3z9u+PAZ22FkJniku1XAs3ZLGsalmC0ipzkp2/BQ=; b=D4kfswdnNORrNRMJeUqHYkCvMF6PIvZxq5wln2i+sUXq/ybUSDZUyMIFaQdO4SKOf7 dt/Z3SS/BvVIGpkKXPsnEFzrU2n/y3+udRrOY0VRm9qrXx4RbL0EMJq+zzgL4/slLnvD OHIU5gqmBGIJj9zU+h2GmCtJAB6HANqWQVKGhfXyc/syTVC2zfPmHafIWBzVKRmhLKMb R9re0tY6MJOi0NmgGbYtUwebnudB2IaCjk6le6CFihflhMS6ZafxOzeQ2FkRzyJr5KfK B/8vEaP1u18Gr69efbnzOU0iVMwAJE7NDV2hi+QgSCrQAfEp0jSt1Raz5rS0jkUsKb97 scjQ== X-Gm-Message-State: AOAM533DqWzLVsE8bJo0sXSNMG2FIvQ0SA+zE7Pze9mJXvF4e4ShQxnf r9io7LDy2UGzqCS1JaiYaOLWtYV2vV0oh3LbqN4= X-Received: by 2002:a1c:964d:: with SMTP id y74mr4655344wmd.154.1592491736234; Thu, 18 Jun 2020 07:48:56 -0700 (PDT) MIME-Version: 1.0 References: <20200618003916.26644-1-gaurav1086@gmail.com> In-Reply-To: <20200618003916.26644-1-gaurav1086@gmail.com> From: Namhyung Kim Date: Thu, 18 Jun 2020 23:48:45 +0900 Message-ID: Subject: Re: [PATCH] [perf] Fix null pointer deference in nest_epollfd To: Gaurav Singh Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Tommi Rantala , Thomas Gleixner , "open list:PERFORMANCE EVENTS SUBSYSTEM" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Jun 18, 2020 at 9:39 AM Gaurav Singh wrote: > > Add a NULL check for worker before dereferencing. Did you actually see a segfault due to this? It seems it's called with NULL only if multiq is false so there should not be a NULL dereference. > > Signed-off-by: Gaurav Singh > --- > tools/perf/bench/epoll-wait.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/tools/perf/bench/epoll-wait.c b/tools/perf/bench/epoll-wait.c > index 75dca9773186..42983eb7f82e 100644 > --- a/tools/perf/bench/epoll-wait.c > +++ b/tools/perf/bench/epoll-wait.c > @@ -239,6 +239,9 @@ static void *workerfn(void *arg) > > static void nest_epollfd(struct worker *w) > { > + if (!w) > + return; > + > unsigned int i; > struct epoll_event ev; > int efd = multiq ? w->epollfd : epollfd; Maybe it's more intuitive to check w instead of multiq here. Thanks Namhyung > -- > 2.17.1 >