bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 143 insertions, 0 deletions

diff --git a/net/rxrpc/tests/Makefile b/net/rxrpc/tests/Makefile
new file mode 100644
index 000000000..4f5100880
--- /dev/null
+++ b/net/rxrpc/tests/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_AF_RXRPC_KUNIT_TEST) += rxrpc_kunit.o
diff --git a/net/rxrpc/tests/rxrpc_kunit.c b/net/rxrpc/tests/rxrpc_kunit.c
new file mode 100644
index 000000000..95fd05a07
--- /dev/null
+++ b/net/rxrpc/tests/rxrpc_kunit.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Unit tests for RxRPC crypto functions
+ *
+ * Copyright 2026 Google LLC
+ */
+#include "../ar-internal.h"
+#include <crypto/des.h>
+#include <kunit/test.h>
+
+struct fcrypt_pcbc_testvec {
+	u8 key[FCRYPT_BSIZE];
+	u8 iv[FCRYPT_BSIZE];
+	const u8 *ptext; /* plaintext */
+	const u8 *ctext; /* ciphertext */
+	size_t nblocks; /* length of ptext and ctext in blocks */
+};
+
+/* FCrypt-PCBC test vectors */
+static const struct fcrypt_pcbc_testvec fcrypt_pcbc_testvecs[] = {
+	{
+		/* http://www.openafs.org/pipermail/openafs-devel/2000-December/005320.html */
+		.key = "\x00\x00\x00\x00\x00\x00\x00\x00",
+		.iv = "\x00\x00\x00\x00\x00\x00\x00\x00",
+		.ptext = "\x00\x00\x00\x00\x00\x00\x00\x00",
+		.ctext = "\x0E\x09\x00\xC7\x3E\xF7\xED\x41",
+		.nblocks = 1,
+	},
+	{
+		.key = "\x11\x44\x77\xAA\xDD\x00\x33\x66",
+		.iv = "\x00\x00\x00\x00\x00\x00\x00\x00",
+		.ptext = "\x12\x34\x56\x78\x9A\xBC\xDE\xF0",
+		.ctext = "\xD8\xED\x78\x74\x77\xEC\x06\x80",
+		.nblocks = 1,
+	},
+	{
+		/* From Arla */
+		.key = "\xf0\xe1\xd2\xc3\xb4\xa5\x96\x87",
+		.iv = "\xfe\xdc\xba\x98\x76\x54\x32\x10",
+		.ptext = "The quick brown fox jumps over the lazy dogs.\0\0",
+		.ctext = "\x00\xf0\x0e\x11\x75\xe6\x23\x82"
+			 "\xee\xac\x98\x62\x44\x51\xe4\x84"
+			 "\xc3\x59\xd8\xaa\x64\x60\xae\xf7"
+			 "\xd2\xd9\x13\x79\x72\xa3\x45\x03"
+			 "\x23\xb5\x62\xd7\x0c\xf5\x27\xd1"
+			 "\xf8\x91\x3c\xac\x44\x22\x92\xef",
+		.nblocks = 6,
+	},
+	{
+		.key = "\xfe\xdc\xba\x98\x76\x54\x32\x10",
+		.iv = "\xf0\xe1\xd2\xc3\xb4\xa5\x96\x87",
+		.ptext = "The quick brown fox jumps over the lazy dogs.\0\0",
+		.ctext = "\xca\x90\xf5\x9d\xcb\xd4\xd2\x3c"
+			 "\x01\x88\x7f\x3e\x31\x6e\x62\x9d"
+			 "\xd8\xe0\x57\xa3\x06\x3a\x42\x58"
+			 "\x2a\x28\xfe\x72\x52\x2f\xdd\xe0"
+			 "\x19\x89\x09\x1c\x2a\x8e\x8c\x94"
+			 "\xfc\xc7\x68\xe4\x88\xaa\xde\x0f",
+		.nblocks = 6,
+	}
+};
+
+static void test_fcrypt_pcbc(struct kunit *test)
+{
+	u8 data[48];
+
+	for (size_t i = 0; i < ARRAY_SIZE(fcrypt_pcbc_testvecs); i++) {
+		const struct fcrypt_pcbc_testvec *tv = &fcrypt_pcbc_testvecs[i];
+		const size_t nblocks = tv->nblocks;
+		const size_t len = nblocks * FCRYPT_BSIZE;
+		struct fcrypt_key key;
+
+		KUNIT_ASSERT_GE(test, sizeof(data), len);
+
+		fcrypt_preparekey(&key, tv->key);
+
+		/* out-of-place encryption */
+		fcrypt_pcbc_encrypt(&key, tv->iv, tv->ptext, data, nblocks);
+		KUNIT_ASSERT_MEMEQ(test, tv->ctext, data, len);
+
+		/* in-place encryption */
+		memcpy(data, tv->ptext, len);
+		fcrypt_pcbc_encrypt(&key, tv->iv, data, data, nblocks);
+		KUNIT_ASSERT_MEMEQ(test, tv->ctext, data, len);
+
+		/* out-of-place decryption */
+		fcrypt_pcbc_decrypt(&key, tv->iv, tv->ctext, data, nblocks);
+		KUNIT_ASSERT_MEMEQ(test, tv->ptext, data, len);
+
+		/* in-place decryption */
+		memcpy(data, tv->ctext, len);
+		fcrypt_pcbc_decrypt(&key, tv->iv, data, data, nblocks);
+		KUNIT_ASSERT_MEMEQ(test, tv->ptext, data, len);
+	}
+}
+
+static void test_des_pcbc(struct kunit *test)
+{
+	/* This was generated from the original pcbc(des) crypto API code. */
+	static const u8 expected_ptext[24] =
+		"\xc8\xe2\x3c\xdf\x80\x61\x8a\xad\xa5\x52\xb4\x20"
+		"\x74\x32\x1f\xe4\x2c\x15\x7d\x21\x57\xda\x3f\x31";
+	u8 key[8];
+	union {
+		__le64 w;
+		u8 b[8];
+	} iv;
+	u8 data[24];
+	struct des_ctx ctx;
+	int err;
+
+	for (int i = 0; i < 8; i++) {
+		key[i] = i;
+		iv.b[i] = 255 - i;
+	}
+	for (int i = 0; i < sizeof(data); i++)
+		data[i] = i;
+
+	err = des_expand_key(&ctx, key, sizeof(key));
+	KUNIT_ASSERT_EQ(test, 0, err);
+
+	des_pcbc_decrypt_inplace(&ctx, iv.w, data, sizeof(data));
+	KUNIT_ASSERT_MEMEQ(test, expected_ptext, data, sizeof(data));
+}
+
+static struct kunit_case rxrpc_test_cases[] = {
+	KUNIT_CASE(test_fcrypt_pcbc),
+	KUNIT_CASE(test_des_pcbc),
+	{},
+};
+
+static struct kunit_suite rxrpc_test_suite = {
+	.name = "rxrpc",
+	.test_cases = rxrpc_test_cases,
+};
+kunit_test_suite(rxrpc_test_suite);
+
+MODULE_DESCRIPTION("Unit tests for RxRPC crypto functions");
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
+MODULE_LICENSE("GPL");