[PATCH 6/8] perf machine: Reset errno before strtol in guest kernel map creation

[Arnaldo Carvalho de Melo]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

machines__create_guest_kernel_maps() checks errno == ERANGE after
strtol() to detect overflow, but does not clear errno first.  A stale
ERANGE from an earlier library call (e.g. scandir internals) causes
valid numeric directory names to be incorrectly skipped.

Set errno = 0 before strtol() so only the current conversion can
trigger the ERANGE check.

Fixes: a1645ce12adb ("perf: 'perf kvm' tool for monitoring guest performance from host")
Reported-by: sashiko-bot <sashiko-bot@xxxxxxxxxx>
Cc: Zhang, Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/machine.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 83d38637afe34fc9..1700130adedb3a89 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1258,6 +1258,7 @@ int machines__create_guest_kernel_maps(struct machines *machines)
 				/* Filter out . and .. */
 				continue;
 			}
+			errno = 0;
 			pid = (pid_t)strtol(namelist[i]->d_name, &endp, 10);
 			if ((*endp != '\0') ||
 			    (endp == namelist[i]->d_name) ||
-- 
2.55.0