perf/x86/intel: Fix memory corruption

Through:

  validate_event()
    x86_pmu.get_event_constraints(.idx=-1)
      tfa_get_event_constraints()
        dyn_constraint()

cpuc->constraint_list[-1] is used, which is an obvious out-of-bound access.

In this case, simply skip the TFA constraint code, there is no event
constraint with just PMC3, therefore the code will never result in the
empty set.

Fixes: 400816f60c54 ("perf/x86/intel: Implement support for TSX Force Abort")
Reported-by: Tony Jones <tonyj@suse.com>
Reported-by: "DSouza, Nelson" <nelson.dsouza@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Tony Jones <tonyj@suse.com>
Tested-by: "DSouza, Nelson" <nelson.dsouza@intel.com>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Cc: stable@kernel.org
Link: https://lkml.kernel.org/r/20190314130705.441549378@infradead.org

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 35102ecdfc8d5debd884581bb1d40e2a9029a59f..92dfeb343a6ae2fb86ed0d63f4247963521ec4f8 100644 (file)
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3410,7 +3410,7 @@ tfa_get_event_constraints(struct cpu_hw_events *cpuc, int idx,
        /*
         * Without TFA we must not use PMC3.
         */
-       if (!allow_tsx_force_abort && test_bit(3, c->idxmsk)) {
+       if (!allow_tsx_force_abort && test_bit(3, c->idxmsk) && idx >= 0) {
                c = dyn_constraint(cpuc, c, idx);
                c->idxmsk64 &= ~(1ULL << 3);
                c->weight--;