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

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 <[email protected]>
Tested-by: Vince Weaver <[email protected]>
Signed-off-by: Kan Liang <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/events/intel/uncore_snb.c b/arch/x86/events/intel/uncore_snb.c
index 81195cca7eaecb5da2ff7924ea0a0e5d994c27cf..a3dcc12bef4ab3a67aab29c6acf3480920e06952 100644 (file)
--- 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)