[PATCH 6.18.y] selftests/landlock: Fix snprintf truncation checks in test files

[Sasha Levin <sashal@kernel.org>]

From: Wang Yan <wangyan01@kylinos.cn>

[ Upstream commit 8e4c736cffdd6b133f6498e0d40ba60dc6819d43 ]

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>
Reviewed-by: Günther Noack <gnoack@google.com>
Link: https://patch.msgid.link/20260626070016.61049-1-wangyan01@kylinos.cn
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
[ sashal: Adjusted context for the earlier TCP-specific audit helpers with their existing names and formatting. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 dcf63b2f822e9..aa6df1b4d42e6 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 8f3a780d354b7..822c23425d15a 100644
--- a/tools/testing/selftests/landlock/net_test.c
+++ b/tools/testing/selftests/landlock/net_test.c
@@ -2067,7 +2067,7 @@ static int matches_log_tcp(const int audit_fd, const char *const blockers,
 
 	log_match_len = snprintf(log_match, sizeof(log_match), log_template,
 				 blockers, dir_addr, addr, dir_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,
@@ -2192,7 +2192,7 @@ static int matches_log_tcp_bound(int audit_fd, const char *const addr,
 
 	log_match_len = snprintf(log_match, sizeof(log_match), log_template,
 				 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 4e356334ecb74..22133c5ae6c56 100644
--- a/tools/testing/selftests/landlock/ptrace_test.c
+++ b/tools/testing/selftests/landlock/ptrace_test.c
@@ -446,7 +446,7 @@ 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,
-- 
2.53.0