From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 15 May 2014 18:23:48 +0000 (+0200)
Subject: perf: Limit perf_event_attr::sample_period to 63 bits
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=95090e8a573c7743a2b0d800c4c52fac581e5bbe;p=linux-edison.git

perf: Limit perf_event_attr::sample_period to 63 bits

commit 0819b2e30ccb93edf04876237b6205eef84ec8d2 upstream.

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 <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-p25fhunibl4y3qi0zuqmyf4b@git.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 0a29beef35f..a130e4a1d50 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6590,6 +6590,9 @@ 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;
 	}
 
 	/*