[PATCH] selftests/landlock: Fix snprintf truncation checks in test files

[PATCH] selftests/landlock: Fix snprintf truncation checks in test files

[Wang Yan]

Commit b566f7a4f0e4 ("selftests/landlock: Fix snprintf truncation checks
in audit helpers") fixed the truncation detection in audit.h by changing
the comparison from ">" to ">=" to correctly handle the edge case where
snprintf returns a value equal to the buffer size.

However, the same pattern exists in ptrace_test.c, audit_test.c, and
net_test.c and was not fixed.  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. The existing ">" check therefore fails to detect truncation when
the return value equals the buffer size.

Fix these remaining instances to use ">=" for truncation detection,
matching the fix in audit.h.

Fixes: 6a500b22971c ("selftests/landlock: Add tests for audit flags and domain IDs")
Signed-off-by: Haofeng Li <lihaofeng@kylinos.cn>
Signed-off-by: Wang Yan <wangyan01@kylinos.cn>
---
 tools/testing/selftests/landlock/audit_test.c  | 2 +-
 tools/testing/selftests/landlock/net_test.c    | 4 ++--
 tools/testing/selftests/landlock/ptrace_test.c | 2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/landlock/audit_test.c b/tools/testing/selftests/landlock/audit_test.c
index 72b5612375dd..4bea8c880a4d 100644
--- a/tools/testing/selftests/landlock/audit_test.c
+++ b/tools/testing/selftests/landlock/audit_test.c
@@ -31,7 +31,7 @@ static int matches_log_signal(struct __test_metadata *const _metadata,
 
 	log_match_len =
 		snprintf(log_match, sizeof(log_match), log_template, opid);
-	if (log_match_len > sizeof(log_match))
+	if (log_match_len >= sizeof(log_match))
 		return -E2BIG;
 
 	return audit_match_record(audit_fd, AUDIT_LANDLOCK_ACCESS, log_match,
diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
index 2ed1f76b7a8b..aebeafd80466 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -2777,7 +2777,7 @@ static int matches_auditlog(const int audit_fd, const char *const blockers,
 		log_match_len = snprintf(log_match, sizeof(log_match),
 					 log_with_addrport_tmpl, blockers,
 					 dir_addr, addr, dir_port, port);
-	if (log_match_len > sizeof(log_match))
+	if (log_match_len >= sizeof(log_match))
 		return -E2BIG;
 
 	return audit_match_record(audit_fd, AUDIT_LANDLOCK_ACCESS, log_match,
@@ -3072,7 +3072,7 @@ static int matches_log_connect_bound(int audit_fd, const char *const blockers,
 
 	log_match_len = snprintf(log_match, sizeof(log_match), log_template,
 				 blockers, addr, lport, addr, dport);
-	if (log_match_len > sizeof(log_match))
+	if (log_match_len >= sizeof(log_match))
 		return -E2BIG;
 
 	return audit_match_record(audit_fd, AUDIT_LANDLOCK_ACCESS, log_match,
diff --git a/tools/testing/selftests/landlock/ptrace_test.c b/tools/testing/selftests/landlock/ptrace_test.c
index 4f64c90583cd..65cf2d82f721 100644
--- a/tools/testing/selftests/landlock/ptrace_test.c
+++ b/tools/testing/selftests/landlock/ptrace_test.c
@@ -302,7 +302,7 @@ static int matches_log_ptrace(struct __test_metadata *const _metadata,
 
 	log_match_len =
 		snprintf(log_match, sizeof(log_match), log_template, opid);
-	if (log_match_len > sizeof(log_match))
+	if (log_match_len >= sizeof(log_match))
 		return -E2BIG;
 
 	return audit_match_record(audit_fd, AUDIT_LANDLOCK_ACCESS, log_match,
-- 
2.25.1