From: Ian Rogers <irogers@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
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: [PATCH v1] libperf mmap: In user mmap rdpmc avoid undefined behavior
Date: Sun, 14 Sep 2025 11:24:37 -0700 [thread overview]
Message-ID: <20250914182437.1959331-1-irogers@google.com> (raw)
A shift left of a signed 64-bit s64 may overflow and result in
undefined behavior caught by ubsan. Switch to a u64 instead.
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 reply other threads:[~2025-09-14 18:24 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-14 18:24 Ian Rogers [this message]
2025-10-02 18:04 ` [PATCH v1] libperf mmap: In user mmap rdpmc avoid undefined behavior Arnaldo Carvalho de Melo
2026-11-13 19:44 ` Rob Herring
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