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perf: Limit perf_event_attr::sample_period to 63 bits

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Vince reported that using a large sample_period (one with bit 63 set)
results in wreckage since while the sample_period is fundamentally
unsigned (negative periods don't make sense) the way we implement
things very much rely on signed logic.

So limit sample_period to 63 bits to avoid tripping over this.

Reported-by: Vince Weaver <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
This commit is contained in:
Peter Zijlstra authored and Thomas Gleixner committed 2014-05-19 21:44:55 +09:00
1 parent a45e903842
commit 0819b2e30c
1 file changed
+3
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kernel/events/core.c
+3
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@@ -7029,6 +7029,9 @@ SYSCALL_DEFINE5(perf_event_open,
if (attr.freq) {
if (attr.sample_freq > sysctl_perf_event_sample_rate)
return -EINVAL;
} else {
if (attr.sample_period & (1ULL << 63))
return -EINVAL;
}
/*