linux-kernel - Re: [GIT PULL] tracing: Have filter check for balanced ops

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Message-ID: <20150625003510.1ea5a750@grimm.local.home>
Date:	Thu, 25 Jun 2015 00:35:10 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [GIT PULL] tracing: Have filter check for balanced ops

On Thu, 25 Jun 2015 00:03:02 -0400
Sasha Levin <sasha.levin@...cle.com> wrote:

> On 06/17/2015 08:36 AM, Steven Rostedt wrote:
> > Linus,
> > 
> > Vince Weaver reported a warning when he added perf event filters
> > into his fuzzer tests. There's a missing check of balanced
> > operations when parenthesis are used, and this triggers a WARN_ON()
> > and when reading the failure, the filter reports no failure occurred.
> 
> Hey Steven,
> 
> My fuzzings are hitting the warning added by this patch:

Yes, Vince said he was able to hit it as well. But the warning itself
is useless if you don't supply what filter was used to trigger it.

-- Steve


> 
> [2175114.187536] WARNING: CPU: 16 PID: 10388 at kernel/trace/trace_events_filter.c:1388 replace_preds+0x814/0x2140()
> [2175114.190213] Modules linked in:
> [2175114.191111] CPU: 16 PID: 10388 Comm: trinity-c48 Not tainted 4.1.0-next-20150623-sasha-00039-ga1eb83a-dirty #2280
> [2175114.194463]  ffff880a23350000 000000006a8e22d4 ffff880a2335f878 ffffffffabc8cfa3
> [2175114.196547]  0000000000000000 0000000000000000 ffff880a2335f8c8 ffffffffa21ebd36
> [2175114.198604]  ffff880e60fe09e0 ffffffffa24608f4 ffff880e61b14830 ffff880e60fe09d8
> [2175114.200666] Call Trace:
> [2175114.201377]  [<ffffffffabc8cfa3>] dump_stack+0x4f/0x7b
> [2175114.202793]  [<ffffffffa21ebd36>] warn_slowpath_common+0xc6/0x120
> [2175114.206235]  [<ffffffffa21ebf7a>] warn_slowpath_null+0x1a/0x20
> [2175114.207819]  [<ffffffffa24608f4>] replace_preds+0x814/0x2140
> [2175114.216433]  [<ffffffffa24638aa>] create_filter+0x15a/0x210
> [2175114.231529]  [<ffffffffa246406b>] apply_event_filter+0x28b/0x780
> [2175114.241196]  [<ffffffffa2450306>] event_filter_write+0x106/0x1c0
> [2175114.242823]  [<ffffffffa260dd48>] do_loop_readv_writev+0x128/0x1e0
> [2175114.248901]  [<ffffffffa261051e>] do_readv_writev+0x5ae/0x6c0
> [2175114.256760]  [<ffffffffa2610742>] vfs_writev+0x72/0xb0
> [2175114.258134]  [<ffffffffa2613bb4>] SyS_pwritev+0x1b4/0x220
> [2175114.261291]  [<ffffffffabcf9962>] tracesys_phase2+0x88/0x8d
> 
> 
> Thanks,
> Sasha

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