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perf: Ensure that IOC_OUTPUT isn't used to create multi-writer buffers 

Since we want to ensure buffers only have a single
writer, we must avoid creating one with multiple.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20100521090710.528215873@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
hifive-unleashed-5.1
Peter Zijlstra 2010-05-20 14:35:15 +02:00 committed by Ingo Molnar
parent 1c024eca51
commit 0f139300c9
1 changed files with 19 additions and 0 deletions
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19
kernel/perf_event.c
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@ -4920,6 +4920,13 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
int fput_needed = 0;
int ret = -EINVAL;
/*
* Don't allow output of inherited per-task events. This would
* create performance issues due to cross cpu access.
*/
if (event->cpu == -1 && event->attr.inherit)
return -EINVAL;
if (!output_fd)
goto set;
@ -4940,6 +4947,18 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
if (event->data)
goto out;
/*
* Don't allow cross-cpu buffers
*/
if (output_event->cpu != event->cpu)
goto out;
/*
* If its not a per-cpu buffer, it must be the same task.
*/
if (output_event->cpu == -1 && output_event->ctx != event->ctx)
goto out;
atomic_long_inc(&output_file->f_count);
set: