linux-kernel - [tip:perf/urgent] perf/x86/uncore: Fix crash by removing bogus event_list[] handling for SNB client uncore IMC

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Message-ID: <tip-c499336cea8bbe15554c6fcea2138658c5395bfe@git.kernel.org>
Date:   Wed, 16 Nov 2016 04:08:18 -0800
From:   tip-bot for Kan Liang <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, vincent.weaver@...ne.edu,
        linux-kernel@...r.kernel.org, kan.liang@...el.com,
        peterz@...radead.org, torvalds@...ux-foundation.org,
        jolsa@...hat.com, tglx@...utronix.de,
        alexander.shishkin@...ux.intel.com, hpa@...or.com,
        eranian@...gle.com, acme@...hat.com
Subject: [tip:perf/urgent] perf/x86/uncore: Fix crash by removing bogus
 event_list[] handling for SNB client uncore IMC

Commit-ID:  c499336cea8bbe15554c6fcea2138658c5395bfe
Gitweb:     http://git.kernel.org/tip/c499336cea8bbe15554c6fcea2138658c5395bfe
Author:     Kan Liang <kan.liang@...el.com>
AuthorDate: Tue, 15 Nov 2016 13:40:10 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 16 Nov 2016 09:46:35 +0100

perf/x86/uncore: Fix crash by removing bogus event_list[] handling for SNB client uncore IMC

Vince Weaver reported the following bug when KASAN is enabled:

 [  205.748005] BUG: KASAN: slab-out-of-bounds in snb_uncore_imc_event_del+0x6c/0xa0 at addr ffff8800caa43768
 [  205.758324] Read of size 8 by task perf_fuzzer/6618

It's caused by accessing box->event_list.

For client IMC, there are no generic counters. It defines its own fixed
free running counters. So event_list and n_events are unused.

They can be removed safely, which fixes the bug.

( There's still the separate question of how uninitialized state snuck into
  this data structure - but that's a separate fix. )

Reported-by: Vince Weaver <vincent.weaver@...ne.edu>
Tested-by: Vince Weaver <vincent.weaver@...ne.edu>
Signed-off-by: Kan Liang <kan.liang@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: acme@...nel.org
Cc: davej@...emonkey.org.uk
Cc: dvyukov@...gle.com
Cc: eranian@...il.com
Link: http://lkml.kernel.org/r/1479235210-29090-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/events/intel/uncore_snb.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/arch/x86/events/intel/uncore_snb.c b/arch/x86/events/intel/uncore_snb.c
index 81195cc..a3dcc12 100644
--- a/arch/x86/events/intel/uncore_snb.c
+++ b/arch/x86/events/intel/uncore_snb.c
@@ -490,24 +490,12 @@ static int snb_uncore_imc_event_add(struct perf_event *event, int flags)
 
 	snb_uncore_imc_event_start(event, 0);
 
-	box->n_events++;
-
 	return 0;
 }
 
 static void snb_uncore_imc_event_del(struct perf_event *event, int flags)
 {
-	struct intel_uncore_box *box = uncore_event_to_box(event);
-	int i;
-
 	snb_uncore_imc_event_stop(event, PERF_EF_UPDATE);
-
-	for (i = 0; i < box->n_events; i++) {
-		if (event == box->event_list[i]) {
-			--box->n_events;
-			break;
-		}
-	}
 }
 
 int snb_pci2phy_map_init(int devid)