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perf hwmon: Guard label read against empty or failed reads

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hwmon_pmu__read_events() reads label files with read() into a stack
buffer, strips trailing newlines, then checks buf[0] == '\0'.  When
read() returns 0 (empty file) or -1 (error), the buffer is never
written, so buf[0] reads uninitialized stack memory.  If the garbage
byte is non-zero, the code falls through to strdup(buf) which copies
arbitrary stack data as the label string.

Fix by checking read_len <= 0 before accessing buf contents, closing
the fd and skipping the entry.

Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Fixes: 53cc0b351e ("perf hwmon_pmu: Add a tool PMU exposing events from hwmon in sysfs")
Cc: Ian Rogers <irogers@google.com>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2026-06-08 07:03:04 -03:00
parent 51cdb188ed
commit 34d3d93fac
1 changed files with 5 additions and 2 deletions
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7
tools/perf/util/hwmon_pmu.c
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@ -295,8 +295,11 @@ static int hwmon_pmu__read_events(struct hwmon_pmu *pmu)
while (read_len > 0 && buf[read_len - 1] == '\n')
read_len--;
if (read_len > 0)
buf[read_len] = '\0';
if (read_len <= 0) {
close(fd);
continue;
}
buf[read_len] = '\0';
if (buf[0] == '\0') {
pr_debug("hwmon_pmu: empty label file %s %s\n",