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Subject[tip:perf/urgent] perf/x86/intel: Fix memory corruption
Commit-ID:  ede271b059463731cbd6dffe55ffd70d7dbe8392
Gitweb: https://git.kernel.org/tip/ede271b059463731cbd6dffe55ffd70d7dbe8392
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 14 Mar 2019 14:01:14 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 15 Mar 2019 12:22:51 +0100

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

---
arch/x86/events/intel/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 35102ecdfc8d..92dfeb343a6a 100644
--- 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--;
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