Re: [PATCH 1/3] perf, evlist: Fix access of freed id arrays

[Jiri Olsa]

On Mon, Sep 23, 2019 at 04:33:37PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 
> I'm not fully sure if this is the correct fix, but without this
> I get crashes on more complex perf stat metric usages. The problem
> is that part of the state gets freed when a weak group fails,
> but then is later still used. Just don't free the ids, we're
> going to reuse them anyways on the weak group retry.
> 
> For example:
> 
> % perf stat -M IpB,IpCall,IpTB,IPC,Retiring_SMT,Frontend_Bound_SMT,Kernel_Utilization,CPU_Utilization --metric-only -a -I 1000 sleep 2
> 
> crashes and gives in valgrind:
> 
> =21527== Invalid write of size 8
> ==21527==    at 0x4EE582: hlist_add_head (list.h:644)
> ==21527==    by 0x4EFD3C: perf_evlist__id_hash (evlist.c:477)
> ==21527==    by 0x4EFD99: perf_evlist__id_add (evlist.c:483)
> ==21527==    by 0x4EFF15: perf_evlist__id_add_fd (evlist.c:524)
> ==21527==    by 0x4FC693: store_evsel_ids (evsel.c:2969)
> ==21527==    by 0x4FC76C: perf_evsel__store_ids (evsel.c:2986)
> ==21527==    by 0x450DA7: __run_perf_stat (builtin-stat.c:519)
> ==21527==    by 0x451285: run_perf_stat (builtin-stat.c:636)
> ==21527==    by 0x454619: cmd_stat (builtin-stat.c:1966)
> ==21527==    by 0x4D557D: run_builtin (perf.c:310)
> ==21527==    by 0x4D57EA: handle_internal_command (perf.c:362)
> ==21527==    by 0x4D5931: run_argv (perf.c:406)
> ==21527==  Address 0x12e3f008 is 104 bytes inside a block of size 2,056 free'd
> ==21527==    at 0x4839A0C: free (vg_replace_malloc.c:540)
> ==21527==    by 0x627139: xyarray__delete (xyarray.c:32)
> ==21527==    by 0x4F6BE4: perf_evsel__free_id (evsel.c:1253)
> ==21527==    by 0x4FA11F: evsel__close (evsel.c:1994)
> ==21527==    by 0x4F30A3: perf_evlist__reset_weak_group (evlist.c:1783)
> ==21527==    by 0x450B47: __run_perf_stat (builtin-stat.c:466)
> ==21527==    by 0x451285: run_perf_stat (builtin-stat.c:636)
> ==21527==    by 0x454619: cmd_stat (builtin-stat.c:1966)
> ==21527==    by 0x4D557D: run_builtin (perf.c:310)
> ==21527==    by 0x4D57EA: handle_internal_command (perf.c:362)
> ==21527==    by 0x4D5931: run_argv (perf.c:406)
> ==21527==    by 0x4D5CAE: main (perf.c:531)
> ==21527==  Block was alloc'd at
> ==21527==    at 0x483AB1A: calloc (vg_replace_malloc.c:762)
> ==21527==    by 0x627024: zalloc (zalloc.c:8)
> ==21527==    by 0x627088: xyarray__new (xyarray.c:10)
> ==21527==    by 0x4F6B20: perf_evsel__alloc_id (evsel.c:1237)
> ==21527==    by 0x4FC74E: perf_evsel__store_ids (evsel.c:2983)
> ==21527==    by 0x450DA7: __run_perf_stat (builtin-stat.c:519)
> ==21527==    by 0x451285: run_perf_stat (builtin-stat.c:636)
> ==21527==    by 0x454619: cmd_stat (builtin-stat.c:1966)
> ==21527==    by 0x4D557D: run_builtin (perf.c:310)
> ==21527==    by 0x4D57EA: handle_internal_command (perf.c:362)
> ==21527==    by 0x4D5931: run_argv (perf.c:406)
> ==21527==    by 0x4D5CAE: main (perf.c:531)
> 
> Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> ---
>  tools/perf/util/evlist.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 095924aa186b..765303553041 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1780,7 +1780,7 @@ struct evsel *perf_evlist__reset_weak_group(struct evlist *evsel_list,
>  			is_open = false;
>  		if (c2->leader == leader) {
>  			if (is_open)
> -				evsel__close(c2);
> +				perf_evsel__close(&evsel->core);

id/sample_id arrays are not created when evsel is open but
we free it at close

for now this fix seems correct to me.. we are moving id/sample_id
arrays under libperf, I'll make a note to check on close and reopen
of evsel and add some tests for that

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

thanks,
jirka

>  			c2->leader = c2;
>  			c2->core.nr_members = 0;
>  		}
> -- 
> 2.21.0
>