Messages in this thread | | | Date | Fri, 20 Apr 2018 11:36:26 -0400 | From | Steven Rostedt <> | Subject | Re: [RFC] trace_events: Fix kernel crash while using empty filter with perf |
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On Fri, 20 Apr 2018 20:37:58 +0530 Ravi Bangoria <ravi.bangoria@linux.ibm.com> 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 <ravi.bangoria@linux.ibm.com>
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; > }
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