[LTP] [PATCH v2 08/33] keyctl16: Test KEYCTL_GET_SECURITY truncated copy

[Andrea Cervesato]

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

Test KEYCTL_GET_SECURITY truncated copy behavior: verify that calling
with a 1-byte buffer receives exactly one byte while the return value
still reports the full label length.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 runtest/syscalls                            |  1 +
 testcases/kernel/syscalls/keyctl/.gitignore |  1 +
 testcases/kernel/syscalls/keyctl/keyctl16.c | 74 +++++++++++++++++++++++++++++
 3 files changed, 76 insertions(+)

diff --git a/runtest/syscalls b/runtest/syscalls
index da901baae..89c8a95af 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -733,6 +733,7 @@ keyctl12 keyctl12
 keyctl13 keyctl13
 keyctl14 keyctl14
 keyctl15 keyctl15
+keyctl16 keyctl16
 
 kcmp01 kcmp01
 kcmp02 kcmp02
diff --git a/testcases/kernel/syscalls/keyctl/.gitignore b/testcases/kernel/syscalls/keyctl/.gitignore
index 852fee4ea..c351716d0 100644
--- a/testcases/kernel/syscalls/keyctl/.gitignore
+++ b/testcases/kernel/syscalls/keyctl/.gitignore
@@ -13,3 +13,4 @@
 /keyctl13
 /keyctl14
 /keyctl15
+/keyctl16
diff --git a/testcases/kernel/syscalls/keyctl/keyctl16.c b/testcases/kernel/syscalls/keyctl/keyctl16.c
new file mode 100644
index 000000000..f5662e326
--- /dev/null
+++ b/testcases/kernel/syscalls/keyctl/keyctl16.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2026 Andrea Cervesato <andrea.cervesato@suse.com>
+ */
+
+/*\
+ * Test ``KEYCTL_GET_SECURITY`` truncated copy of :manpage:`keyctl(2)`.
+ *
+ * ``KEYCTL_GET_SECURITY`` returns the full length of the label, but unlike
+ * ``KEYCTL_DESCRIBE`` the kernel performs a truncated copy when the user
+ * buffer is too small.
+ *
+ * [Algorithm]
+ *
+ * - verify a one byte buffer receives exactly one byte while the full
+ *   length is still returned
+ */
+
+#include "keyctl_common.h"
+
+#define KEY_DESC	"ltpkeyctl16"
+#define PAYLOAD		"payload"
+#define BUF_SIZE	128
+
+static key_serial_t key;
+static long sec_len;
+static char buf[BUF_SIZE];
+
+static void setup(void)
+{
+	SAFE_KEYCTL(KEYCTL_JOIN_SESSION_KEYRING, 0, 0, 0, 0);
+
+	key = new_user_key(KEY_DESC, PAYLOAD, sizeof(PAYLOAD),
+			   KEY_SPEC_PROCESS_KEYRING);
+	SAFE_KEYCTL(KEYCTL_SETPERM, key, KEY_PERM_SET, 0, 0);
+
+	TEST(keyctl(KEYCTL_GET_SECURITY, key, (unsigned long)NULL, 0, 0));
+	if (TST_RET < 0)
+		tst_brk(TBROK | TTERRNO, "KEYCTL_GET_SECURITY failed");
+
+	sec_len = TST_RET;
+}
+
+static void run(void)
+{
+	size_t i;
+
+	memset(buf, 0xAA, sizeof(buf));
+	TST_EXP_EQ_LI_SILENT(keyctl(KEYCTL_GET_SECURITY, key,
+				    (unsigned long)buf, 1, 0), sec_len);
+	if (!TST_PASS)
+		return;
+
+	if (buf[0] == (char)0xAA) {
+		tst_res(TFAIL, "nothing was copied into the buffer");
+		return;
+	}
+
+	for (i = 1; i < sizeof(buf); i++) {
+		if (buf[i] != (char)0xAA) {
+			tst_res(TFAIL, "copy overran the buffer at offset %zu",
+				i);
+			return;
+		}
+	}
+
+	tst_res(TPASS, "exactly one byte copied, full length %ld returned",
+		sec_len);
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.test_all = run,
+};

-- 
2.51.0