* [PATCH v1] libperf mmap: In user mmap rdpmc avoid undefined behavior
@ 2025-09-14 18:24 Ian Rogers
2025-10-02 18:04 ` Arnaldo Carvalho de Melo
0 siblings, 1 reply; 2+ messages in thread
From: Ian Rogers @ 2025-09-14 18:24 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter, Kan Liang, linux-perf-users,
linux-kernel
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
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH v1] libperf mmap: In user mmap rdpmc avoid undefined behavior
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
0 siblings, 0 replies; 2+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-10-02 18:04 UTC (permalink / raw)
To: Ian Rogers
Cc: Peter Zijlstra, Ingo Molnar, Namhyung Kim, Mark Rutland,
Alexander Shishkin, Jiri Olsa, Adrian Hunter, Kan Liang,
linux-perf-users, linux-kernel
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
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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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
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