Messages in this thread |  | | From | Vince Weaver <> | Date | Mon, 6 Jan 2020 13:09:56 -0500 (EST) | Subject | Re: [PATCH] perf: correctly handle failed perf_get_aux_event() (was: Re: [perf] perf_event_open() sometimes returning 0) |
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On Mon, 6 Jan 2020, Mark Rutland wrote:
> On Thu, Jan 02, 2020 at 02:22:47PM -0500, Vince Weaver wrote: > > On Thu, 2 Jan 2020, Vince Weaver wrote: > > > Vince, does the below (untested) patch work for you?
yes, this patch fixes things for me.
Tested-by: Vince Weaver <vincent.weaver@maine.edu>
> ---->8---- > From c79f31b42aaf85f3a924af9218794b3bc8b79892 Mon Sep 17 00:00:00 2001 > From: Mark Rutland <mark.rutland@arm.com> > Date: Mon, 6 Jan 2020 11:51:06 +0000 > Subject: [PATCH] perf: correctly handle failed perf_get_aux_event() > > Vince reports a worrying issue: > > | so I was tracking down some odd behavior in the perf_fuzzer which turns > | out to be because perf_even_open() sometimes returns 0 (indicating a file > | descriptor of 0) even though as far as I can tell stdin is still open. > > ... and further the cause: > > | error is triggered if aux_sample_size has non-zero value. > | > | seems to be this line in kernel/events/core.c: > | > | if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) > | goto err_locked; > | > | (note, err is never set) > > This seems to be a thinko in commit: > > ab43762ef010967e ("perf: Allow normal events to output AUX data") > > ... and we should probably return -EINVAL here, as this should only > happen when the new event is mis-configured or does not have a > compatible aux_event group leader. > > Fixes: ab43762ef010967e ("perf: Allow normal events to output AUX data") > Reported-by: Vince Weaver <vincent.weaver@maine.edu> > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> > --- > kernel/events/core.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index a1f8bde19b56..2173c23c25b4 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -11465,8 +11465,10 @@ SYSCALL_DEFINE5(perf_event_open, > } > } > > - if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) > + if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) { > + err = -EINVAL; > goto err_locked; > + } > > /* > * Must be under the same ctx::mutex as perf_install_in_context(), > -- > 2.11.0 > >
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