Re: [PATCH v3 04/22] perf dso: Hold lock when accessing nsinfo

Jiri Olsa
2022-02-12T11:30:47Z

On Fri, Feb 11, 2022 at 02:33:57AM -0800, Ian Rogers wrote:
> There may be threads racing to update dso->nsinfo:
> https://lore.kernel.org/linux-perf-users/CAP-5=fWZH20L4kv-BwVtGLwR=Em3AOOT+Q4QGivvQuYn5AsPRg@mail.gmail.com/
> Holding the dso->lock avoids use-after-free, memory leaks and other
> such bugs. Apply the fix in:
> https://lore.kernel.org/linux-perf-users/20211118193714.2293728-1-irogers@google.com/
> of there being a missing nsinfo__put now that the accesses are data race
> free.
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
> tools/perf/builtin-inject.c | 4 ++++
> tools/perf/util/dso.c | 5 ++++-
> tools/perf/util/map.c | 3 +++
> tools/perf/util/probe-event.c | 2 ++
> tools/perf/util/symbol.c | 2 +-
> 5 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index fbf43a454cba..bede332bf0e2 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -363,8 +363,10 @@ static struct dso *findnew_dso(int pid, int tid, const char *filename,
> }
>
> if (dso) {
> + BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
> nsinfo__put(dso->nsinfo);
> dso->nsinfo = nsi;
> + pthread_mutex_unlock(&dso->lock);
> } else
> nsinfo__put(nsi);
>
> @@ -547,7 +549,9 @@ static int dso__read_build_id(struct dso *dso)
> if (dso->has_build_id)
> return 0;
>
> + BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
> nsinfo__mountns_enter(dso->nsinfo, &nsc);
> + pthread_mutex_unlock(&dso->lock);

so this separates nsinfo__mountns_enter and nsinfo__put,
should we care also about nsinfo__mountns_exit?

jirka

> if (filename__read_build_id(dso->long_name, &dso->bid) > 0)
> dso->has_build_id = true;
> nsinfo__mountns_exit(&nsc);
> diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
> index 6beccffeef7b..b2f570adba35 100644
> --- a/tools/perf/util/dso.c
> +++ b/tools/perf/util/dso.c
> @@ -548,8 +548,11 @@ static int open_dso(struct dso *dso, struct machine *machine)
> int fd;
> struct nscookie nsc;
>
> - if (dso->binary_type != DSO_BINARY_TYPE__BUILD_ID_CACHE)
> + if (dso->binary_type != DSO_BINARY_TYPE__BUILD_ID_CACHE) {
> + BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
> nsinfo__mountns_enter(dso->nsinfo, &nsc);
> + pthread_mutex_unlock(&dso->lock);
> + }
> fd = __open_dso(dso, machine);
> if (dso->binary_type != DSO_BINARY_TYPE__BUILD_ID_CACHE)
> nsinfo__mountns_exit(&nsc);
> diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
> index 8af693d9678c..ae99b52502d5 100644
> --- a/tools/perf/util/map.c
> +++ b/tools/perf/util/map.c
> @@ -192,7 +192,10 @@ struct map *map__new(struct machine *machine, u64 start, u64 len,
> if (!(prot & PROT_EXEC))
> dso__set_loaded(dso);
> }
> + BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
> + nsinfo__put(dso->nsinfo);
> dso->nsinfo = nsi;
> + pthread_mutex_unlock(&dso->lock);
>
> if (build_id__is_defined(bid))
> dso__set_build_id(dso, bid);
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index a834918a0a0d..7444e689ece7 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -180,8 +180,10 @@ struct map *get_target_map(const char *target, struct nsinfo *nsi, bool user)
>
> map = dso__new_map(target);
> if (map && map->dso) {
> + BUG_ON(pthread_mutex_lock(&map->dso->lock) != 0);
> nsinfo__put(map->dso->nsinfo);
> map->dso->nsinfo = nsinfo__get(nsi);
> + pthread_mutex_unlock(&map->dso->lock);
> }
> return map;
> } else {
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 43f47532696f..a504346feb05 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1774,6 +1774,7 @@ int dso__load(struct dso *dso, struct map *map)
> char newmapname[PATH_MAX];
> const char *map_path = dso->long_name;
>
> + BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
> perfmap = strncmp(dso->name, "/tmp/perf-", 10) == 0;
> if (perfmap) {
> if (dso->nsinfo && (dso__find_perf_map(newmapname,
> @@ -1783,7 +1784,6 @@ int dso__load(struct dso *dso, struct map *map)
> }
>
> nsinfo__mountns_enter(dso->nsinfo, &nsc);
> - BUG_ON(pthread_mutex_lock(&dso->lock) != 0);
>
> /* check again under the dso->lock */
> if (dso__loaded(dso)) {
> --
> 2.35.1.265.g69c8d7142f-goog
>