linux-kernel - RE: [PATCH 4.14 31/34] perf/x86/intel: Fix memory corruption

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Date:   Mon, 18 Mar 2019 20:29:37 +0000
From:   "DSouza, Nelson" <nelson.dsouza@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Tony Jones <tonyj@...e.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "eranian@...gle.com" <eranian@...gle.com>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "stable@...nel.org" <stable@...nel.org>
Subject: RE: [PATCH 4.14 31/34] perf/x86/intel: Fix memory corruption

With the patch, the kernel crash is not seen on 4.14, 4.19 and 4.20 kernels.

-----Original Message-----
From: DSouza, Nelson 
Sent: Monday, March 18, 2019 11:21 AM
To: 'Greg Kroah-Hartman' <gregkh@...uxfoundation.org>; linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org; Tony Jones <tonyj@...e.com>; Peter Zijlstra (Intel) <peterz@...radead.org>; Thomas Gleixner <tglx@...utronix.de>; eranian@...gle.com; jolsa@...hat.com; stable@...nel.org
Subject: RE: [PATCH 4.14 31/34] perf/x86/intel: Fix memory corruption

Hi Greg,

I was able to reproduce the kernel crash on 4.14, 4.19 and 4.20 kernels. Will apply your patches and re-test.

Thanks,
Nelson

-----Original Message-----
From: Greg Kroah-Hartman [mailto:gregkh@...uxfoundation.org] 
Sent: Monday, March 18, 2019 2:26 AM
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; stable@...r.kernel.org; Tony Jones <tonyj@...e.com>; DSouza, Nelson <nelson.dsouza@...el.com>; Peter Zijlstra (Intel) <peterz@...radead.org>; Thomas Gleixner <tglx@...utronix.de>; eranian@...gle.com; jolsa@...hat.com; stable@...nel.org
Subject: [PATCH 4.14 31/34] perf/x86/intel: Fix memory corruption

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

------------------

From: Peter Zijlstra <peterz@...radead.org>

commit ede271b059463731cbd6dffe55ffd70d7dbe8392 upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3262,7 +3262,7 @@ tfa_get_event_constraints(struct cpu_hw_
 	/*
 	 * 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--;