linux-kernel - Re: [PATCH v2 07/18] perf env: Remove unnecessary NULL tests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAP-5=fX1f022Z052mOxgJODg_jOPCqHScjZam2_3YwUXqriO4A@mail.gmail.com>
Date:   Mon, 9 Oct 2023 09:33:32 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Namhyung Kim <namhyung@...nel.org>
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 07/18] perf env: Remove unnecessary NULL tests

On Sun, Oct 8, 2023 at 11:14 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Thu, Oct 5, 2023 at 4:09 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > clang-tidy was warning:
> > ```
> > util/env.c:334:23: warning: Access to field 'nr_pmu_mappings' results in a dereference of a null pointer (loaded from variable 'env') [clang-analyzer-core.NullDereference]
> >         env->nr_pmu_mappings = pmu_num;
> > ```
> >
> > As functions are called potentially when !env was true. This condition
> > could never be true as it would produce a segv, so remove the
> > unnecessary NULL tests and silence clang-tidy.
>
> IIRC !env was to handle live sessions like perf top
> or when it doesn't have a perf data file.  Anyway,
> it doesn't seem to work anymore.

I trust the analyzer here and it would be better to crash earlier,
from env being NULL, than in a particular conditional branch. Like
you, I wasn't able to find a failure from removing the checks.

Thanks,
Ian

> Thanks,
> Namhyung
>
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/util/env.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c
> > index a164164001fb..44140b7f596a 100644
> > --- a/tools/perf/util/env.c
> > +++ b/tools/perf/util/env.c
> > @@ -457,7 +457,7 @@ const char *perf_env__cpuid(struct perf_env *env)
> >  {
> >         int status;
> >
> > -       if (!env || !env->cpuid) { /* Assume local operation */
> > +       if (!env->cpuid) { /* Assume local operation */
> >                 status = perf_env__read_cpuid(env);
> >                 if (status)
> >                         return NULL;
> > @@ -470,7 +470,7 @@ int perf_env__nr_pmu_mappings(struct perf_env *env)
> >  {
> >         int status;
> >
> > -       if (!env || !env->nr_pmu_mappings) { /* Assume local operation */
> > +       if (!env->nr_pmu_mappings) { /* Assume local operation */
> >                 status = perf_env__read_pmu_mappings(env);
> >                 if (status)
> >                         return 0;
> > @@ -483,7 +483,7 @@ const char *perf_env__pmu_mappings(struct perf_env *env)
> >  {
> >         int status;
> >
> > -       if (!env || !env->pmu_mappings) { /* Assume local operation */
> > +       if (!env->pmu_mappings) { /* Assume local operation */
> >                 status = perf_env__read_pmu_mappings(env);
> >                 if (status)
> >                         return NULL;
> > --
> > 2.42.0.609.gbb76f46606-goog
> >