[LTP] [PATCH v2 03/33] keyctl11: Test KEYCTL_DESCRIBE with exact buffer size

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Test KEYCTL_DESCRIBE when called with a buffer sized exactly to the
full description length: verify the string is copied completely
including the terminating NUL byte.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 runtest/syscalls                            |  1 +
 testcases/kernel/syscalls/keyctl/.gitignore |  1 +
 testcases/kernel/syscalls/keyctl/keyctl11.c | 62 +++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/runtest/syscalls b/runtest/syscalls
index bf4c0d46e..7c9042471 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -728,6 +728,7 @@ keyctl07 keyctl07
 keyctl08 keyctl08
 keyctl09 keyctl09
 keyctl10 keyctl10
+keyctl11 keyctl11
 
 kcmp01 kcmp01
 kcmp02 kcmp02
diff --git a/testcases/kernel/syscalls/keyctl/.gitignore b/testcases/kernel/syscalls/keyctl/.gitignore
index 08b2d101d..4974fe48d 100644
--- a/testcases/kernel/syscalls/keyctl/.gitignore
+++ b/testcases/kernel/syscalls/keyctl/.gitignore
@@ -8,3 +8,4 @@
 /keyctl08
 /keyctl09
 /keyctl10
+/keyctl11
diff --git a/testcases/kernel/syscalls/keyctl/keyctl11.c b/testcases/kernel/syscalls/keyctl/keyctl11.c
new file mode 100644
index 000000000..4dd0be7ca
--- /dev/null
+++ b/testcases/kernel/syscalls/keyctl/keyctl11.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Andrea Cervesato <andrea.cervesato@suse.com>
+ */
+
+/*\
+ * Test ``KEYCTL_DESCRIBE`` of :manpage:`keyctl(2)` with exact buffer size.
+ *
+ * [Algorithm]
+ *
+ * - describe a key into a buffer sized exactly to the full string length,
+ *   verify full string copy including terminating NUL byte
+ */
+
+#include "keyctl_common.h"
+
+static key_serial_t key;
+static long desc_len;
+static char *buf;
+
+static void setup(void)
+{
+	SAFE_KEYCTL(KEYCTL_JOIN_SESSION_KEYRING, 0, 0, 0, 0);
+
+	key = new_user_key("k", "payload", 7, KEY_SPEC_PROCESS_KEYRING);
+	SAFE_KEYCTL(KEYCTL_SETPERM, key, KEY_PERM_SET, 0, 0);
+
+	TEST(keyctl(KEYCTL_DESCRIBE, key, (unsigned long)NULL, 0, 0));
+	if (TST_RET < 0)
+		tst_brk(TBROK | TTERRNO, "KEYCTL_DESCRIBE failed");
+
+	desc_len = TST_RET;
+	buf = SAFE_MALLOC(desc_len);
+}
+
+static void cleanup(void)
+{
+	free(buf);
+}
+
+static void run(void)
+{
+	memset(buf, 0, desc_len);
+	TST_EXP_EQ_LI_SILENT(keyctl(KEYCTL_DESCRIBE, key, (unsigned long)buf,
+				    desc_len, 0), desc_len);
+	if (!TST_PASS)
+		return;
+
+	if (buf[desc_len - 1] != '\0') {
+		tst_res(TFAIL, "description is not NUL terminated");
+		return;
+	}
+
+	tst_res(TPASS, "full description including NUL fits exact %ld byte buffer",
+		desc_len);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = run,
+};

-- 
2.51.0