linux-kernel - [tip:perf/urgent] perf/x86/intel: Fix memory corruption

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Message-ID: <tip-ede271b059463731cbd6dffe55ffd70d7dbe8392@git.kernel.org>
Date:   Fri, 15 Mar 2019 04:29:07 -0700
From:   tip-bot for Peter Zijlstra <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, linux-kernel@...r.kernel.org,
        peterz@...radead.org, hpa@...or.com, tglx@...utronix.de,
        nelson.dsouza@...el.com, tonyj@...e.com
Subject: [tip:perf/urgent] perf/x86/intel: Fix memory corruption

Commit-ID:  ede271b059463731cbd6dffe55ffd70d7dbe8392
Gitweb:     https://git.kernel.org/tip/ede271b059463731cbd6dffe55ffd70d7dbe8392
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Thu, 14 Mar 2019 14:01:14 +0100
Committer:  Thomas Gleixner <tglx@...utronix.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@...e.com>
Reported-by: "DSouza, Nelson" <nelson.dsouza@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Tony Jones <tonyj@...e.com>
Tested-by: "DSouza, Nelson" <nelson.dsouza@...el.com>
Cc: eranian@...gle.com
Cc: jolsa@...hat.com
Cc: stable@...nel.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--;