[3.11.y.z extended stable] Patch "perf: Limit perf_event_attr::sample_period to 63 bits" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    perf: Limit perf_event_attr::sample_period to 63 bits

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 372fffa1e68467e2ccc4a10181a23ed015867f55 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz at infradead.org>
Date: Thu, 15 May 2014 20:23:48 +0200
Subject: 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 at maine.edu>
Signed-off-by: Peter Zijlstra <peterz at infradead.org>
Link: http://lkml.kernel.org/n/tip-p25fhunibl4y3qi0zuqmyf4b@git.kernel.org
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/events/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 9c511b4296db..fe0c665c54d2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6816,6 +6816,9 @@ 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;
 	}

 	/*
--
1.9.1