[PATCH AUTOSEL for 4.14 047/100] powerpc/perf: Fix oops when grouping different pmu events

Sasha Levin
2018-01-28T23:07:52Z

From: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>

[ Upstream commit 5aa04b3eb6fca63d2e9827be656dcadc26d54e11 ]

When user tries to group imc (In-Memory Collections) event with
normal event, (sometime) kernel crashes with following log:

Faulting instruction address: 0x00000000
[link register ] c00000000010ce88 power_check_constraints+0x128/0x980
...
c00000000010e238 power_pmu_event_init+0x268/0x6f0
c0000000002dc60c perf_try_init_event+0xdc/0x1a0
c0000000002dce88 perf_event_alloc+0x7b8/0xac0
c0000000002e92e0 SyS_perf_event_open+0x530/0xda0
c00000000000b004 system_call+0x38/0xe0

'event_base' field of 'struct hw_perf_event' is used as flags for
normal hw events and used as memory address for imc events. While
grouping these two types of events, collect_events() tries to
interpret imc 'event_base' as a flag, which causes a corruption
resulting in a crash.

Consider only those events which belongs to 'perf_hw_context' in
collect_events().

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Reviewed-By: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
arch/powerpc/perf/core-book3s.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index b4209a68b85d..fce545774d50 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1419,7 +1419,7 @@ static int collect_events(struct perf_event *group, int max_count,
int n = 0;
struct perf_event *event;

- if (!is_software_event(group)) {
+ if (group->pmu->task_ctx_nr == perf_hw_context) {
if (n >= max_count)
return -1;
ctrs[n] = group;
@@ -1427,7 +1427,7 @@ static int collect_events(struct perf_event *group, int max_count,
events[n++] = group->hw.config;
}
list_for_each_entry(event, &group->sibling_list, group_entry) {
- if (!is_software_event(event) &&
+ if (event->pmu->task_ctx_nr == perf_hw_context &&
event->state != PERF_EVENT_STATE_OFF) {
if (n >= max_count)
return -1;
--
2.11.0