From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754123AbeC1Poi (ORCPT ); Wed, 28 Mar 2018 11:44:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:49810 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754044AbeC1Poh (ORCPT ); Wed, 28 Mar 2018 11:44:37 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 39BA82172B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Wed, 28 Mar 2018 11:44:34 -0400 From: Steven Rostedt To: Wang Yu Cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] ftrace: fix task's invalid comm of <...> when big pid Message-ID: <20180328114434.3a05d3bc@gandalf.local.home> In-Reply-To: <20180328113522.21b4298b@gandalf.local.home> References: <1522240347-24465-1-git-send-email-yuwang@linux.alibaba.com> <20180328113522.21b4298b@gandalf.local.home> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 28 Mar 2018 11:35:22 -0400 Steven Rostedt wrote: > On Wed, 28 Mar 2018 20:32:27 +0800 > Wang Yu wrote: > > > when pid is bigger than PID_MAX_DEFAULT, the comm of task > > is <...>, it is better use pid_max to compare > > > > Signed-off-by: Wang Yu > > --- > > kernel/trace/trace.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > mode change 100644 => 100755 kernel/trace/trace.c > > > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > old mode 100644 > > new mode 100755 > > index 20a2300..0d4bc7a > > --- a/kernel/trace/trace.c > > +++ b/kernel/trace/trace.c > > @@ -1976,7 +1976,7 @@ static void __trace_find_cmdline(int pid, char comm[]) > > return; > > } > > > > - if (pid > PID_MAX_DEFAULT) { > > + if (pid > pid_max) { > > Thanks! this probably should go to stable. I take that back. This patch can cause a buffer overflow access. If you looked at the line after this check, you would see: if (pid > PID_MAX_DEFAULT) { strcpy(comm, "<...>"); return; } map = savedcmd->map_pid_to_cmdline[pid]; And if you looked to see what map_pid_to_cmdline is: struct saved_cmdlines_buffer { unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1]; Your patch will access memory past the end of that array, and cause a bug. If you want to support more than PID_MAX_DEFAULT, a lot more needs to change than this. And a change like this isn't going to go to stable. What you can do is make that map_pid_to_cmdline array bigger. -- Steve > > -- Steve > > > strcpy(comm, "<...>"); > > return; > > } >