From: Ian Rogers <irogers@google.com>
Date: Sun, 14 Sep 2025 18:24:37 +0000 (-0700)
Subject: libperf mmap: In user mmap rdpmc avoid undefined behavior
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8dc364fa484df22d301a16148d1b356931d0cbb0;p=users%2Fhch%2Fmisc.git

libperf mmap: In user mmap rdpmc avoid undefined behavior

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>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---

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;