[PATCH] perf/x86/uncore: remove event_list for snb client uncore IMC

[PATCH] perf/x86/uncore: remove event_list for snb client uncore IMC

[kan.liang]

From: Kan Liang <kan.liang@intel.com>

A BUG was found by perf_fuzzer after enabled KASAN.
[  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
[  205.763589] CPU: 0 PID: 6618 Comm: perf_fuzzer Not tainted 4.9.0-rc5
 #4
[  205.770721] Hardware name: LENOVO 10AM000AUS/SHARKBAY, BIOS
FBKT72AUS 01/26/2014
[  205.778689]  ffff8800c3c479b8 ffffffff816bb796 ffff88011ec00600
ffff8800caa43580
[  205.786759]  ffff8800c3c479e0 ffffffff812fb961 ffff8800c3c47a78
ffff8800caa43580
[  205.794850]  ffff8800caa43580 ffff8800c3c47a68 ffffffff812fbbd8
ffff8800c3c47a28
[  205.802911] Call Trace:
[  205.805559]  [<ffffffff816bb796>] dump_stack+0x63/0x8d
[  205.811135]  [<ffffffff812fb961>] kasan_object_err+0x21/0x70
[  205.817267]  [<ffffffff812fbbd8>] kasan_report_error+0x1d8/0x4c0
[  205.823752]  [<ffffffff81133275>] ? __lock_is_held+0x75/0xc0
[  205.829868]  [<ffffffff81025b12>] ?
snb_uncore_imc_read_counter+0x42/0x50
[  205.837198]  [<ffffffff810222e2>] ?
uncore_perf_event_update+0xe2/0x160
[  205.844337]  [<ffffffff812fc319>] kasan_report+0x39/0x40
[  205.850085]  [<ffffffff81025e3c>] ?
snb_uncore_imc_event_del+0x6c/0xa0

It's caused by accessing box->event_list.

For client IMC, there is no generic counters. It defines its own fixed
free running counters. So event_list and n_events are unused. They can
be removed safely.

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Tested-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Kan Liang <kan.liang@intel.com>
---
 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)
-- 
2.5.5

Re: [PATCH] perf/x86/uncore: remove event_list for snb client uncore IMC

[Ingo Molnar]

* kan.liang@intel.com <kan.liang@intel.com> wrote:

> From: Kan Liang <kan.liang@intel.com>
> 
> A BUG was found by perf_fuzzer after enabled KASAN.
> [  205.748005] BUG: KASAN: slab-out-of-bounds in
> snb_uncore_imc_event_del+0x6c/0xa0 at addr ffff8800caa43768

> Reported-by: Vince Weaver <vincent.weaver@maine.edu>
> Tested-by: Vince Weaver <vincent.weaver@maine.edu>
> Signed-off-by: Kan Liang <kan.liang@intel.com>
> ---
>  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;
> -		}
> -	}

I'll apply this fix - but could we please also make sure box->event_list[] 
_always_ get initialized to a sane state?

If it had a proper zero initial value in box->n_events the bug would not have 
triggered. So struct intel_uncore_box initialization appears to be sloppy,
and that should be looked at as well...

Thanks,

	Ingo

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

[tip-bot for Kan Liang]

Commit-ID:  c499336cea8bbe15554c6fcea2138658c5395bfe
Gitweb:     http://git.kernel.org/tip/c499336cea8bbe15554c6fcea2138658c5395bfe
Author:     Kan Liang <kan.liang@intel.com>
AuthorDate: Tue, 15 Nov 2016 13:40:10 -0500
Committer:  Ingo Molnar <mingo@kernel.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@maine.edu>
Tested-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@kernel.org
Cc: davej@codemonkey.org.uk
Cc: dvyukov@google.com
Cc: eranian@gmail.com
Link: http://lkml.kernel.org/r/1479235210-29090-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.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)

RE: [PATCH] perf/x86/uncore: remove event_list for snb client uncore IMC

[Liang, Kan]

> 
> * kan.liang@intel.com <kan.liang@intel.com> wrote:
> 
> > From: Kan Liang <kan.liang@intel.com>
> >
> > A BUG was found by perf_fuzzer after enabled KASAN.
> > [  205.748005] BUG: KASAN: slab-out-of-bounds in
> > snb_uncore_imc_event_del+0x6c/0xa0 at addr ffff8800caa43768
> 
> > Reported-by: Vince Weaver <vincent.weaver@maine.edu>
> > Tested-by: Vince Weaver <vincent.weaver@maine.edu>
> > Signed-off-by: Kan Liang <kan.liang@intel.com>
> > ---
> >  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;
> > -		}
> > -	}
> 
> I'll apply this fix - but could we please also make sure box->event_list[]
> _always_ get initialized to a sane state?
> 

box is allocated by kzalloc_node. It should be always initialized to a
sane state.

But the previous code only update n_events, and forget to update
event_list in event add. That triggers the bug in event del.

Thanks,
Kan

> If it had a proper zero initial value in box->n_events the bug would not
> have triggered. So struct intel_uncore_box initialization appears to be
> sloppy, and that should be looked at as well...
> 
> Thanks,
> 
> 	Ingo