[ 3.5.y.z extended stable ] Patch "ARM: 7809/1: perf: fix event validation for software group" has been added to staging queue

[Luis Henriques]

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

    ARM: 7809/1: perf: fix event validation for software group

to the linux-3.5.y-queue branch of the 3.5.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-3.5.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 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 3178b728e9972c8c94ec3956fc277ca48cd6aa54 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon at arm.com>
Date: Wed, 7 Aug 2013 23:39:41 +0100
Subject: [PATCH] ARM: 7809/1: perf: fix event validation for software group
 leaders

commit c95eb3184ea1a3a2551df57190c81da695e2144b upstream.

It is possible to construct an event group with a software event as a
group leader and then subsequently add a hardware event to the group.
This results in the event group being validated by adding all members
of the group to a fake PMU and attempting to allocate each event on
their respective PMU.

Unfortunately, for software events wthout a corresponding arm_pmu, this
results in a kernel crash attempting to dereference the ->get_event_idx
function pointer.

This patch fixes the problem by checking explicitly for software events
and ignoring those in event validation (since they can always be
scheduled). We will probably want to revisit this for 3.12, since the
validation checks don't appear to work correctly when dealing with
multiple hardware PMUs anyway.

Reported-by: Vince Weaver <vincent.weaver at maine.edu>
Tested-by: Vince Weaver <vincent.weaver at maine.edu>
Tested-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/arm/kernel/perf_event.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index c716dbd..3a6fb86 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -324,6 +324,9 @@ validate_event(struct pmu_hw_events *hw_events,
 	struct hw_perf_event fake_event = event->hw;
 	struct pmu *leader_pmu = event->group_leader->pmu;

+	if (is_software_event(event))
+		return 1;
+
 	if (event->pmu != leader_pmu || event->state < PERF_EVENT_STATE_OFF)
 		return 1;

--
1.8.3.2