linux-kernel - Re: [PATCH v2 05/18] perf bench uprobe: Fix potential use of memory after free

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Date:   Sun, 8 Oct 2023 22:51:33 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Yicong Yang <yangyicong@...ilicon.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ming Wang <wangming01@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Yuan Can <yuancan@...wei.com>,
        Ravi Bangoria <ravi.bangoria@....com>,
        James Clark <james.clark@....com>, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v2 05/18] perf bench uprobe: Fix potential use of memory
 after free

On Thu, Oct 5, 2023 at 4:09 PM Ian Rogers <irogers@...gle.com> wrote:
>
> Found by clang-tidy:
> ```
> bench/uprobe.c:98:3: warning: Use of memory after it is freed [clang-analyzer-unix.Malloc]
>                 bench_uprobe_bpf__destroy(skel);
> ```
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>

I'm ok with the change but I think it won't call
bench_uprobe__teardown_bpf_skel() if the setup function
returns a negative value.  Maybe we also need to set the
err in the default case of `switch (bench)` statement.

Thanks,
Namhyung


> ---
>  tools/perf/bench/uprobe.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/tools/perf/bench/uprobe.c b/tools/perf/bench/uprobe.c
> index 914c0817fe8a..5c71fdc419dd 100644
> --- a/tools/perf/bench/uprobe.c
> +++ b/tools/perf/bench/uprobe.c
> @@ -89,6 +89,7 @@ static int bench_uprobe__setup_bpf_skel(enum bench_uprobe bench)
>         return err;
>  cleanup:
>         bench_uprobe_bpf__destroy(skel);
> +       skel = NULL;
>         return err;
>  }
>
> --
> 2.42.0.609.gbb76f46606-goog
>