[PATCH v3 1/5] selftests/landlock: Fix snprintf truncation checks in audit helpers

[Mickaël Salaün]

snprintf() returns the number of characters that would have been
written, excluding the terminating NUL byte.  When the output is
truncated, this return value equals or exceeds the buffer size.  Fix
matches_log_domain_allocated() and matches_log_domain_deallocated() to
detect truncation with ">=" instead of ">".

Cc: Günther Noack <gnoack at google.com>
Cc: stable at vger.kernel.org
Fixes: 6a500b22971c ("selftests/landlock: Add tests for audit flags and domain IDs")
Reviewed-by: Günther Noack <gnoack at google.com>
Signed-off-by: Mickaël Salaün <mic at digikod.net>
---

Changes since v1:
https://lore.kernel.org/r/20260312100444.2609563-8-mic@digikod.net
- New patch (split from the drain fix).
---
 tools/testing/selftests/landlock/audit.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/landlock/audit.h b/tools/testing/selftests/landlock/audit.h
index 44eb433e9666..1049a0582af5 100644
--- a/tools/testing/selftests/landlock/audit.h
+++ b/tools/testing/selftests/landlock/audit.h
@@ -309,7 +309,7 @@ static int __maybe_unused matches_log_domain_allocated(int audit_fd, pid_t pid,
 
 	log_match_len =
 		snprintf(log_match, sizeof(log_match), log_template, pid);
-	if (log_match_len > sizeof(log_match))
+	if (log_match_len >= sizeof(log_match))
 		return -E2BIG;
 
 	return audit_match_record(audit_fd, AUDIT_LANDLOCK_DOMAIN, log_match,
@@ -326,7 +326,7 @@ static int __maybe_unused matches_log_domain_deallocated(
 
 	log_match_len = snprintf(log_match, sizeof(log_match), log_template,
 				 num_denials);
-	if (log_match_len > sizeof(log_match))
+	if (log_match_len >= sizeof(log_match))
 		return -E2BIG;
 
 	return audit_match_record(audit_fd, AUDIT_LANDLOCK_DOMAIN, log_match,
-- 
2.53.0