[PATCH 08/15] perf hwmon: Fix fd check to accept fd 0 in hwmon_pmu__describe_items()

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

hwmon_pmu__describe_items() checks 'if (fd > 0)' after openat(), which
incorrectly rejects fd 0.  While fd 0 is normally stdin, if stdin has
been closed (common in daemon/service contexts), the kernel reuses fd 0
for the next open.  With fd > 0, the sysfs file is not read and the fd
is leaked.

Change to 'if (fd >= 0)' to match the standard openat() error check.

Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Fixes: 53cc0b351ec99278 ("perf hwmon_pmu: Add a tool PMU exposing events from hwmon in sysfs")
Cc: Ian Rogers <irogers@google.com>
Assisted-by: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/hwmon_pmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/hwmon_pmu.c b/tools/perf/util/hwmon_pmu.c
index efd3067a2e591050..ed544dca70c380b2 100644
--- a/tools/perf/util/hwmon_pmu.c
+++ b/tools/perf/util/hwmon_pmu.c
@@ -435,7 +435,7 @@ static size_t hwmon_pmu__describe_items(struct hwmon_pmu *hwm, char *out_buf, si
 			hwmon_item_strs[bit],
 			is_alarm ? "_alarm" : "");
 		fd = openat(dir, buf, O_RDONLY);
-		if (fd > 0) {
+		if (fd >= 0) {
 			ssize_t read_len = read(fd, buf, sizeof(buf) - 1);
 
 			while (read_len > 0 && buf[read_len - 1] == '\n')
-- 
2.54.0