diff options
| author | Arnaldo Carvalho de Melo <acme@redhat.com> | 2026-06-06 20:37:52 -0300 |
|---|---|---|
| committer | Arnaldo Carvalho de Melo <acme@redhat.com> | 2026-06-10 11:38:45 -0300 |
| commit | 0a012113bb3a44482c163f16f4db03ccaa37a339 (patch) | |
| tree | 1541ed1052bdb09de11d9df71ce18a4754d3a962 | |
| parent | f54ce06049bf716f6b1e3a78e72360d583ea2acb (diff) | |
perf tools: Fix get_max_num() size_t underflow on empty sysfs file
get_max_num() reads a sysfs file (cpu/possible, cpu/present, or
node/possible) and scans backward from the end to find the last
number. If the file is empty, filename__read_str() returns num == 0.
The loop `while (--num)` decrements the size_t from 0 to SIZE_MAX,
reading backward across the heap until a comma or hyphen is found
or unmapped memory is hit.
Add an early return for empty files before the backward scan.
Fixes: 7780c25bae59fd04 ("perf tools: Allow ability to map cpus to nodes easily")
Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Ian Rogers <irogers@google.com>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
| -rw-r--r-- | tools/perf/util/cpumap.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c index 21fa781b03cc..1fab00ec4a59 100644 --- a/tools/perf/util/cpumap.c +++ b/tools/perf/util/cpumap.c @@ -448,6 +448,12 @@ static int get_max_num(char *path, int *max) buf[num] = '\0'; + /* empty file — nothing to parse */ + if (num == 0) { + err = -1; + goto out; + } + /* start on the right, to find highest node num */ while (--num) { if ((buf[num] == ',') || (buf[num] == '-')) { |