[PATCH] perf lock contention: Fix msan issue in lock_contention_read()

[PATCH] perf lock contention: Fix msan issue in lock_contention_read()

[Namhyung Kim]

I got a report of a msan failure like below:

  $ sudo perf lock con -ab -- sleep 1
  ...
  ==224416==WARNING: MemorySanitizer: use-of-uninitialized-value
      #0 0x5651160d6c96 in lock_contention_read  util/bpf_lock_contention.c:290:8
      #1 0x565115f90870 in __cmd_contention  builtin-lock.c:1919:3
      #2 0x565115f90870 in cmd_lock  builtin-lock.c:2385:8
      #3 0x565115f03a83 in run_builtin  perf.c:330:11
      #4 0x565115f03756 in handle_internal_command  perf.c:384:8
      #5 0x565115f02d53 in run_argv  perf.c:428:2
      #6 0x565115f02d53 in main  perf.c:562:3
      #7 0x7f43553bc632 in __libc_start_main
      #8 0x565115e865a9 in _start

It was because the 'key' variable is not initialized.  Actually it'd be set
by bpf_map_get_next_key() but msan didn't seem to understand it.  Let's make
msan happy by initializing the variable.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/bpf_lock_contention.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
index 235fc7150545..5927bf0bd92b 100644
--- a/tools/perf/util/bpf_lock_contention.c
+++ b/tools/perf/util/bpf_lock_contention.c
@@ -249,7 +249,7 @@ static const char *lock_contention_get_name(struct lock_contention *con,
 int lock_contention_read(struct lock_contention *con)
 {
 	int fd, stack, err = 0;
-	struct contention_key *prev_key, key;
+	struct contention_key *prev_key, key = {};
 	struct contention_data data = {};
 	struct lock_stat *st = NULL;
 	struct machine *machine = con->machine;
-- 
2.40.0.348.gf938b09366-goog

Re: [PATCH] perf lock contention: Fix msan issue in lock_contention_read()

[Ian Rogers]

On Thu, Mar 23, 2023 at 5:19 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> I got a report of a msan failure like below:
>
>   $ sudo perf lock con -ab -- sleep 1
>   ...
>   ==224416==WARNING: MemorySanitizer: use-of-uninitialized-value
>       #0 0x5651160d6c96 in lock_contention_read  util/bpf_lock_contention.c:290:8
>       #1 0x565115f90870 in __cmd_contention  builtin-lock.c:1919:3
>       #2 0x565115f90870 in cmd_lock  builtin-lock.c:2385:8
>       #3 0x565115f03a83 in run_builtin  perf.c:330:11
>       #4 0x565115f03756 in handle_internal_command  perf.c:384:8
>       #5 0x565115f02d53 in run_argv  perf.c:428:2
>       #6 0x565115f02d53 in main  perf.c:562:3
>       #7 0x7f43553bc632 in __libc_start_main
>       #8 0x565115e865a9 in _start
>
> It was because the 'key' variable is not initialized.  Actually it'd be set
> by bpf_map_get_next_key() but msan didn't seem to understand it.  Let's make
> msan happy by initializing the variable.
>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Acked-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> ---
>  tools/perf/util/bpf_lock_contention.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
> index 235fc7150545..5927bf0bd92b 100644
> --- a/tools/perf/util/bpf_lock_contention.c
> +++ b/tools/perf/util/bpf_lock_contention.c
> @@ -249,7 +249,7 @@ static const char *lock_contention_get_name(struct lock_contention *con,
>  int lock_contention_read(struct lock_contention *con)
>  {
>         int fd, stack, err = 0;
> -       struct contention_key *prev_key, key;
> +       struct contention_key *prev_key, key = {};
>         struct contention_data data = {};
>         struct lock_stat *st = NULL;
>         struct machine *machine = con->machine;
> --
> 2.40.0.348.gf938b09366-goog
>

Re: [PATCH] perf lock contention: Fix msan issue in lock_contention_read()

[Arnaldo Carvalho de Melo]

Em Thu, Mar 23, 2023 at 11:50:57PM -0700, Ian Rogers escreveu:
> On Thu, Mar 23, 2023 at 5:19 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > I got a report of a msan failure like below:
> >
> >   $ sudo perf lock con -ab -- sleep 1
> >   ...
> >   ==224416==WARNING: MemorySanitizer: use-of-uninitialized-value
> >       #0 0x5651160d6c96 in lock_contention_read  util/bpf_lock_contention.c:290:8
> >       #1 0x565115f90870 in __cmd_contention  builtin-lock.c:1919:3
> >       #2 0x565115f90870 in cmd_lock  builtin-lock.c:2385:8
> >       #3 0x565115f03a83 in run_builtin  perf.c:330:11
> >       #4 0x565115f03756 in handle_internal_command  perf.c:384:8
> >       #5 0x565115f02d53 in run_argv  perf.c:428:2
> >       #6 0x565115f02d53 in main  perf.c:562:3
> >       #7 0x7f43553bc632 in __libc_start_main
> >       #8 0x565115e865a9 in _start
> >
> > It was because the 'key' variable is not initialized.  Actually it'd be set
> > by bpf_map_get_next_key() but msan didn't seem to understand it.  Let's make
> > msan happy by initializing the variable.
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> 
> Acked-by: Ian Rogers <irogers@google.com>

Thanks, applied.

- Arnaldo

 
> Thanks,
> Ian
> 
> > ---
> >  tools/perf/util/bpf_lock_contention.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/bpf_lock_contention.c b/tools/perf/util/bpf_lock_contention.c
> > index 235fc7150545..5927bf0bd92b 100644
> > --- a/tools/perf/util/bpf_lock_contention.c
> > +++ b/tools/perf/util/bpf_lock_contention.c
> > @@ -249,7 +249,7 @@ static const char *lock_contention_get_name(struct lock_contention *con,
> >  int lock_contention_read(struct lock_contention *con)
> >  {
> >         int fd, stack, err = 0;
> > -       struct contention_key *prev_key, key;
> > +       struct contention_key *prev_key, key = {};
> >         struct contention_data data = {};
> >         struct lock_stat *st = NULL;
> >         struct machine *machine = con->machine;
> > --
> > 2.40.0.348.gf938b09366-goog
> >

-- 

- Arnaldo