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Date:   Thu, 5 Mar 2020 16:58:43 -0300
From:   Arnaldo Carvalho de Melo <acme@redhat.com>
To:     zhe.he@windriver.com
Cc:     Andi Kleen <ak@linux.intel.com>, jolsa@kernel.org, meyerk@hpe.com,
        Jiri Olsa <jolsa@redhat.com>, linux-kernel@vger.kernel.org,
        acme@kernel.org
Subject: Re: [PATCH] perf: Fix crash due to null pointer dereference when
 iterating cpu map
Message-ID: <20200305195843.GA7262@redhat.com>
References: <1583405239-352868-1-git-send-email-zhe.he@windriver.com>
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 <20200305183206.GA1454533@tassilo.jf.intel.com>
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Em Thu, Mar 05, 2020 at 10:32:06AM -0800, Andi Kleen escreveu:
> On Thu, Mar 05, 2020 at 12:27:55PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Mar 05, 2020 at 06:47:19PM +0800, zhe.he@windriver.com escreveu:
> > > From: He Zhe <zhe.he@windriver.com>
> > > 
> > > NULL pointer may be passed to perf_cpu_map__cpu and then cause the
> > > following crash.
> > > 
> > > perf ftrace -G start_kernel ls
> > > failed to set tracing filters
> > > [  208.710716] perf[341]: segfault at 4 ip 00000000567c7c98
> > >                sp 00000000ff937ae0 error 4 in perf[56630000+1b2000]
> > > [  208.724778] Code: fc ff ff e8 aa 9b 01 00 8d b4 26 00 00 00 00 8d
> > >                      76 00 55 89 e5 83 ec 18 65 8b 0d 14 00 00 00 89
> > >                      4d f4 31 c9 8b 45 08 8b9
> > > Segmentation fault
> > 
> > I'm not being able to repro this here, what is the tree you are using?
> 
> I believe that's the same bug that Jann Horn reported recently for perf trace.
> I thought the patch for that went in.

Ok, Zhe, that patch is at the end of this message, and it is in:

[acme@five perf]$ git tag --contains cb71f7d43ece3d5a4f400f510c61b2ec7c9ce9a1 | grep ^v
v5.6-rc1
v5.6-rc2
v5.6-rc3
v5.6-rc4
[acme@five perf]$

Can you try with that?

- Arnaldo

commit cb71f7d43ece3d5a4f400f510c61b2ec7c9ce9a1
Author: Jiri Olsa <jolsa@kernel.org>
Date:   Fri Jan 10 16:15:37 2020 +0100

    libperf: Setup initial evlist::all_cpus value
    
    Jann Horn reported crash in perf ftrace because evlist::all_cpus isn't
    initialized if there's evlist without events, which is the case for perf
    ftrace.
    
    Adding initial initialization of evlist::all_cpus from given cpus,
    regardless of events in the evlist.
    
    Fixes: 7736627b865d ("perf stat: Use affinity for closing file descriptors")
    Reported-by: Jann Horn <jannh@google.com>
    Signed-off-by: Jiri Olsa <jolsa@kernel.org>
    Acked-by: Andi Kleen <ak@linux.intel.com>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Michael Petlan <mpetlan@redhat.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Link: http://lore.kernel.org/lkml/20200110151537.153012-1-jolsa@kernel.org
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
index ae9e65aa2491..5b9f2ca50591 100644
--- a/tools/lib/perf/evlist.c
+++ b/tools/lib/perf/evlist.c
@@ -164,6 +164,9 @@ void perf_evlist__set_maps(struct perf_evlist *evlist,
 		evlist->threads = perf_thread_map__get(threads);
 	}
 
+	if (!evlist->all_cpus && cpus)
+		evlist->all_cpus = perf_cpu_map__get(cpus);
+
 	perf_evlist__propagate_maps(evlist);
 }