From 34d3d93fac6d92237cb9d730ca04c37ed361c7a6 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 8 Jun 2026 07:03:04 -0300 Subject: [PATCH] perf hwmon: Guard label read against empty or failed reads 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 Fixes: 53cc0b351ec99278 ("perf hwmon_pmu: Add a tool PMU exposing events from hwmon in sysfs") Cc: Ian Rogers Assisted-by: Claude:claude-opus-4.6 Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/hwmon_pmu.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/hwmon_pmu.c b/tools/perf/util/hwmon_pmu.c index bdcbe887579a..efd3067a2e59 100644 --- a/tools/perf/util/hwmon_pmu.c +++ b/tools/perf/util/hwmon_pmu.c @@ -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",