From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755779AbeDTPg3 (ORCPT ); Fri, 20 Apr 2018 11:36:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:56008 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755603AbeDTPg2 (ORCPT ); Fri, 20 Apr 2018 11:36:28 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ABDBB20C0F 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: Fri, 20 Apr 2018 11:36:26 -0400 From: Steven Rostedt To: Ravi Bangoria Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, jolsa@kernel.org, kamalesh@linux.vnet.ibm.com Subject: Re: [RFC] trace_events: Fix kernel crash while using empty filter with perf Message-ID: <20180420113626.54cb12de@gandalf.local.home> In-Reply-To: <20180420150758.19787-1-ravi.bangoria@linux.ibm.com> References: <20180420150758.19787-1-ravi.bangoria@linux.ibm.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; 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 Fri, 20 Apr 2018 20:37:58 +0530 Ravi Bangoria wrote: > Kernel is crashing when user tries to record 'ftrace:function' event > with empty filter: > > # perf record -e ftrace:function --filter="" ls > > # dmesg > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 > Oops: 0000 [#1] SMP PTI > ... > RIP: 0010:ftrace_profile_set_filter+0x14b/0x2d0 > RSP: 0018:ffffa4a7c0da7d20 EFLAGS: 00010246 > RAX: ffffa4a7c0da7d64 RBX: 0000000000000000 RCX: 0000000000000006 > RDX: 0000000000000000 RSI: 0000000000000092 RDI: ffff8c48ffc968f0 > ... > Call Trace: > _perf_ioctl+0x54a/0x6b0 > ? rcu_all_qs+0x5/0x30 > ... > > After patch: > # perf record -e ftrace:function --filter="" ls > failed to set filter "" on event ftrace:function with 22 (Invalid argument) > > Also, if user tries to echo "" > filter, it used to throw an error. > This behavior got changed by commit 80765597bc58 ("tracing: Rewrite > filter logic to be simpler and faster"). This patch restores the > behavior as a side effect: > > Before patch: > # echo "" > filter > # > > After patch: > # echo "" > filter > bash: echo: write error: Invalid argument > # > > Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster") > Signed-off-by: Ravi Bangoria With my initial testing, this looks like a proper fix. I'll investigate further, and if you don't hear back from me, it means that I took it. I'm still waiting on one other patch before I start the process of testing my current queue to push to Linus. Once I have that one, I'll start testing my queue, and if I take this, it will be part of it. Thanks! -- Steve > --- > kernel/trace/trace_events_filter.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c > index 9b4716bb8bb0..1f951b3df60c 100644 > --- a/kernel/trace/trace_events_filter.c > +++ b/kernel/trace/trace_events_filter.c > @@ -1499,14 +1499,14 @@ static int process_preds(struct trace_event_call *call, > return ret; > } > > - if (!nr_preds) { > - prog = NULL; > - } else { > - prog = predicate_parse(filter_string, nr_parens, nr_preds, > + if (!nr_preds) > + return -EINVAL; > + > + prog = predicate_parse(filter_string, nr_parens, nr_preds, > parse_pred, call, pe); > - if (IS_ERR(prog)) > - return PTR_ERR(prog); > - } > + if (IS_ERR(prog)) > + return PTR_ERR(prog); > + > rcu_assign_pointer(filter->prog, prog); > return 0; > }