linux-kernel - Re: [PATCH v2 10/10] perf symbol: Fix ENOENT case for filename__read_build

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=fWe-Aax42D_9goaX3e-QFpSQBagqWh6ZD+JgLkrMLSe8w@mail.gmail.com>
Date: Fri, 5 Dec 2025 11:40:12 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach <mike.leach@...aro.org>, 
	James Clark <james.clark@...aro.org>, John Garry <john.g.garry@...cle.com>, 
	Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>, 
	Athira Rajeev <atrajeev@...ux.ibm.com>, tanze <tanze@...inos.cn>, 
	Stephen Brennan <stephen.s.brennan@...cle.com>, Andi Kleen <ak@...ux.intel.com>, 
	Chun-Tse Shao <ctshao@...gle.com>, Thomas Falcon <thomas.falcon@...el.com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>, "Dr. David Alan Gilbert" <linux@...blig.org>, 
	Christophe Leroy <christophe.leroy@...roup.eu>, 
	Krzysztof Łopatowski <krzysztof.m.lopatowski@...il.com>, 
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Alexandre Ghiti <alexghiti@...osinc.com>, 
	Haibo Xu <haibo1.xu@...el.com>, Sergei Trofimovich <slyich@...il.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 10/10] perf symbol: Fix ENOENT case for filename__read_build_id

On Mon, Dec 1, 2025 at 12:55 PM Ian Rogers <irogers@...gle.com> wrote:
>
> Some callers of filename__read_build_id assume the error value must be
> -1, fix by making them handle all < 0 values.
>
> If is_regular_file fails in filename__read_build_id then it could be
> the file is missing (ENOENT) and it would be wrong to return
> -EWOULDBLOCK in that case. Fix the logic so -EWOULDBLOCK is only
> reported if other errors with stat haven't occurred.
>
> Fixes: 834ebb5678d7 ("perf tools: Don't read build-ids from non-regular files")

We might want to prioritize this fix.

> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/builtin-buildid-cache.c | 6 ++++--
>  tools/perf/util/symbol.c           | 3 ++-
>  2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
> index c98104481c8a..539e779e3268 100644
> --- a/tools/perf/builtin-buildid-cache.c
> +++ b/tools/perf/builtin-buildid-cache.c
> @@ -276,12 +276,14 @@ static bool dso__missing_buildid_cache(struct dso *dso, int parm __maybe_unused)
>  {
>         char filename[PATH_MAX];
>         struct build_id bid = { .size = 0, };
> +       int err;
>
>         if (!dso__build_id_filename(dso, filename, sizeof(filename), false))
>                 return true;
>
> -       if (filename__read_build_id(filename, &bid) == -1) {

This check here is clearly wrong when -EWOULDBLOCK is returned from
James' change.

> -               if (errno == ENOENT)
> +       err = filename__read_build_id(filename, &bid);
> +       if (err < 0) {
> +               if (err == -ENOENT)
>                         return false;
>
>                 pr_warning("Problems with %s file, consider removing it from the cache\n",
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 76dc5b70350a..f43e30019e21 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -2008,8 +2008,9 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
>         if (!filename)
>                 return -EFAULT;
>
> +       errno = 0;
>         if (!is_regular_file(filename))
> -               return -EWOULDBLOCK;
> +               return errno == 0 ? -EWOULDBLOCK : -errno;

I've made the fix after the other changes as it is simpler to fix in
one filename__read_build_id rather than all the libbfd, .. variants.
If we don't want the series in the short-term perhaps we still want to
carry some parts of this fix.

Thanks,
Ian

>
>         err = kmod_path__parse(&m, filename);
>         if (err)
> --
> 2.52.0.158.g65b55ccf14-goog
>