selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 90 insertions, 0 deletions

diff --git a/drivers/firewire/uapi-test.c b/drivers/firewire/uapi-test.c
new file mode 100644
index 000000000..bc3f10a2e
--- /dev/null
+++ b/drivers/firewire/uapi-test.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// uapi_test.c - An application of Kunit to check layout of structures exposed to user space for
+//		 FireWire subsystem.
+//
+// Copyright (c) 2023 Takashi Sakamoto
+
+#include <kunit/test.h>
+#include <linux/firewire-cdev.h>
+
+// Known issue added at v2.6.27 kernel.
+static void structure_layout_event_response(struct kunit *test)
+{
+#if defined(CONFIG_X86_32)
+	// 4 bytes alignment for aggregate type including 8 bytes storage types.
+	KUNIT_EXPECT_EQ(test, 20, sizeof(struct fw_cdev_event_response));
+#else
+	// 8 bytes alignment for aggregate type including 8 bytes storage types.
+	KUNIT_EXPECT_EQ(test, 24, sizeof(struct fw_cdev_event_response));
+#endif
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_response, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_response, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_response, rcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_response, length));
+	KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_response, data));
+}
+
+// Added at v6.5.
+static void structure_layout_event_request3(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 56, sizeof(struct fw_cdev_event_request3));
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_request3, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_request3, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_request3, tcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_request3, offset));
+	KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_request3, source_node_id));
+	KUNIT_EXPECT_EQ(test, 28, offsetof(struct fw_cdev_event_request3, destination_node_id));
+	KUNIT_EXPECT_EQ(test, 32, offsetof(struct fw_cdev_event_request3, card));
+	KUNIT_EXPECT_EQ(test, 36, offsetof(struct fw_cdev_event_request3, generation));
+	KUNIT_EXPECT_EQ(test, 40, offsetof(struct fw_cdev_event_request3, handle));
+	KUNIT_EXPECT_EQ(test, 44, offsetof(struct fw_cdev_event_request3, length));
+	KUNIT_EXPECT_EQ(test, 48, offsetof(struct fw_cdev_event_request3, tstamp));
+	KUNIT_EXPECT_EQ(test, 56, offsetof(struct fw_cdev_event_request3, data));
+}
+
+// Added at v6.5.
+static void structure_layout_event_response2(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 32, sizeof(struct fw_cdev_event_response2));
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_response2, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_response2, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_response2, rcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_response2, length));
+	KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_response2, request_tstamp));
+	KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_response2, response_tstamp));
+	KUNIT_EXPECT_EQ(test, 32, offsetof(struct fw_cdev_event_response2, data));
+}
+
+// Added at v6.5.
+static void structure_layout_event_phy_packet2(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ(test, 24, sizeof(struct fw_cdev_event_phy_packet2));
+
+	KUNIT_EXPECT_EQ(test, 0, offsetof(struct fw_cdev_event_phy_packet2, closure));
+	KUNIT_EXPECT_EQ(test, 8, offsetof(struct fw_cdev_event_phy_packet2, type));
+	KUNIT_EXPECT_EQ(test, 12, offsetof(struct fw_cdev_event_phy_packet2, rcode));
+	KUNIT_EXPECT_EQ(test, 16, offsetof(struct fw_cdev_event_phy_packet2, length));
+	KUNIT_EXPECT_EQ(test, 20, offsetof(struct fw_cdev_event_phy_packet2, tstamp));
+	KUNIT_EXPECT_EQ(test, 24, offsetof(struct fw_cdev_event_phy_packet2, data));
+}
+
+static struct kunit_case structure_layout_test_cases[] = {
+	KUNIT_CASE(structure_layout_event_response),
+	KUNIT_CASE(structure_layout_event_request3),
+	KUNIT_CASE(structure_layout_event_response2),
+	KUNIT_CASE(structure_layout_event_phy_packet2),
+	{}
+};
+
+static struct kunit_suite structure_layout_test_suite = {
+	.name = "firewire-uapi-structure-layout",
+	.test_cases = structure_layout_test_cases,
+};
+kunit_test_suite(structure_layout_test_suite);
+
+MODULE_DESCRIPTION("FireWire UAPI unit test suite");
+MODULE_LICENSE("GPL");