4.4-stable review patch.  If anyone has any objections, please let me know.


From: Ravi Bangoria <ravi.bango...@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

Signed-off-by: Ravi Bangoria <ravi.bango...@linux.vnet.ibm.com>
Reviewed-By: Madhavan Srinivasan <ma...@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
 arch/powerpc/perf/core-book3s.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1381,7 +1381,7 @@ static int collect_events(struct perf_ev
        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;
@@ -1389,7 +1389,7 @@ static int collect_events(struct perf_ev
                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;

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