Messages in this thread Patch in this message |  | | Date | Mon, 6 Jan 2020 12:03:39 +0000 | From | Mark Rutland <> | Subject | [PATCH] perf: correctly handle failed perf_get_aux_event() (was: Re: [perf] perf_event_open() sometimes returning 0) |
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On Thu, Jan 02, 2020 at 02:22:47PM -0500, Vince Weaver wrote: > On Thu, 2 Jan 2020, Vince Weaver wrote: > > > 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.
Yikes.
> 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)
Looks like that was introduced in commit:
ab43762ef010967e ("perf: Allow normal events to output AUX data")
I guess we should return -EINVAL in this case.
Vince, does the below (untested) patch work for you?
Thanks, Mark.
---->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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