From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Kan Liang <kan.liang@linux.intel.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] libperf mmap: In user mmap rdpmc avoid undefined behavior
Date: Thu, 2 Oct 2025 15:04:53 -0300 [thread overview]
Message-ID: <aN6-xfp4pcnxbnaq@x1> (raw)
In-Reply-To: <20250914182437.1959331-1-irogers@google.com>
On Sun, Sep 14, 2025 at 11:24:37AM -0700, Ian Rogers wrote:
> A shift left of a signed 64-bit s64 may overflow and result in
> undefined behavior caught by ubsan. Switch to a u64 instead.
Thanks, applied to perf-tools-next,
- Arnaldo
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
> tools/lib/perf/mmap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/perf/mmap.c b/tools/lib/perf/mmap.c
> index c1a51d925e0e..ec124eb0ec0a 100644
> --- a/tools/lib/perf/mmap.c
> +++ b/tools/lib/perf/mmap.c
> @@ -508,7 +508,7 @@ int perf_mmap__read_self(struct perf_mmap *map, struct perf_counts_values *count
> idx = READ_ONCE(pc->index);
> cnt = READ_ONCE(pc->offset);
> if (pc->cap_user_rdpmc && idx) {
> - s64 evcnt = read_perf_counter(idx - 1);
> + u64 evcnt = read_perf_counter(idx - 1);
> u16 width = READ_ONCE(pc->pmc_width);
>
> evcnt <<= 64 - width;
> --
> 2.51.0.384.g4c02a37b29-goog
>
next prev parent reply other threads:[~2025-10-02 18:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-14 18:24 [PATCH v1] libperf mmap: In user mmap rdpmc avoid undefined behavior Ian Rogers
2025-10-02 18:04 ` Arnaldo Carvalho de Melo [this message]
2026-11-13 19:44 ` Rob Herring
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