[PATCH] acpi/s3 : fix stack smashing crash for s3 test

[Hector Cao]

when fwts parses /sys/kernel/debug/wakeup_sources, if this file has
any entry with long name (>32), fwts can crash with error :
*** stack smashing detected ***: terminated
this is a gcc stack smashing protection mechanism that is enabled
with the flag -fstack-protection-strong

this issue has been introduced in the commit
- s3: add checking the device signed wakeup events
and delivered in the version V23.09.00

this commit fixes this issue by enforcing the max len of the field
name fscanf can read from the wakeup_sources entries.

BugLink: https://bugs.launchpad.net/fwts/+bug/2092055

Signed-off-by: Hector Cao <hector.cao at canonical.com>
---
 src/acpi/s3/s3.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/acpi/s3/s3.c b/src/acpi/s3/s3.c
index ffdb7165..c46fe72f 100644
--- a/src/acpi/s3/s3.c
+++ b/src/acpi/s3/s3.c
@@ -96,7 +96,8 @@ static int read_wakeup_source(fwts_list *source)
 	/* skip first line */
 	while (c = fgetc(fp), c != '\n' && c != EOF);
 
-	while (fscanf(fp, "%s\t%lu\t\t%lu\t\t%lu\t\t%lu\t\t%ld\t\t%ld\t\t%ld\t\t%ld\t\t%ld\n",
+	/* NB: important to specify the max len fscanf reads for name to avoid stack smashing */
+	while (fscanf(fp, "%31s\t%lu\t\t%lu\t\t%lu\t\t%lu\t\t%ld\t\t%ld\t\t%ld\t\t%ld\t\t%ld\n",
 			name, &active_count, &event_count,
 			&wakeup_count, &expire_count, &active_since,
 			&total_time, &max_time, &last_change,
-- 
2.43.0