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-Tag: upstream/snapshot3+hdmi~2559
X-Git-Url: http://review.tizen.org/git/?p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git;a=commitdiff_plain;h=23d92064081ba10489b7a654b97255d8dfcfa6f4

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 e80611f..e756171 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7025,6 +7025,9 @@ 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;
 	}
 
 	/*