x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 152 insertions, 0 deletions

diff --git a/drivers/firewire/self-id-sequence-helper-test.c b/drivers/firewire/self-id-sequence-helper-test.c
new file mode 100644
index 000000000..eed7a2294
--- /dev/null
+++ b/drivers/firewire/self-id-sequence-helper-test.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+//
+// self-id-sequence-helper-test.c - An application of Kunit to test helpers of self ID sequence.
+//
+// Copyright (c) 2024 Takashi Sakamoto
+
+#include <kunit/test.h>
+
+#include "phy-packet-definitions.h"
+
+static void test_self_id_sequence_enumerator_valid(struct kunit *test)
+{
+	static const u32 valid_sequences[] = {
+		0x00000000,
+		0x00000001, 0x00800000,
+		0x00000001, 0x00800001, 0x00900000,
+		0x00000000,
+	};
+	struct self_id_sequence_enumerator enumerator;
+	const u32 *entry;
+	unsigned int quadlet_count;
+
+	enumerator.cursor = valid_sequences;
+	enumerator.quadlet_count = ARRAY_SIZE(valid_sequences);
+
+	entry = self_id_sequence_enumerator_next(&enumerator, &quadlet_count);
+	KUNIT_EXPECT_PTR_EQ(test, entry, &valid_sequences[0]);
+	KUNIT_EXPECT_EQ(test, quadlet_count, 1);
+	KUNIT_EXPECT_EQ(test, enumerator.quadlet_count, 6);
+
+	entry = self_id_sequence_enumerator_next(&enumerator, &quadlet_count);
+	KUNIT_EXPECT_PTR_EQ(test, entry, &valid_sequences[1]);
+	KUNIT_EXPECT_EQ(test, quadlet_count, 2);
+	KUNIT_EXPECT_EQ(test, enumerator.quadlet_count, 4);
+
+	entry = self_id_sequence_enumerator_next(&enumerator, &quadlet_count);
+	KUNIT_EXPECT_PTR_EQ(test, entry, &valid_sequences[3]);
+	KUNIT_EXPECT_EQ(test, quadlet_count, 3);
+	KUNIT_EXPECT_EQ(test, enumerator.quadlet_count, 1);
+
+	entry = self_id_sequence_enumerator_next(&enumerator, &quadlet_count);
+	KUNIT_EXPECT_PTR_EQ(test, entry, &valid_sequences[6]);
+	KUNIT_EXPECT_EQ(test, quadlet_count, 1);
+	KUNIT_EXPECT_EQ(test, enumerator.quadlet_count, 0);
+
+	entry = self_id_sequence_enumerator_next(&enumerator, &quadlet_count);
+	KUNIT_EXPECT_EQ(test, PTR_ERR(entry), -ENODATA);
+}
+
+static void test_self_id_sequence_enumerator_invalid(struct kunit *test)
+{
+	static const u32 invalid_sequences[] = {
+		0x00000001,
+	};
+	struct self_id_sequence_enumerator enumerator;
+	const u32 *entry;
+	unsigned int count;
+
+	enumerator.cursor = invalid_sequences;
+	enumerator.quadlet_count = ARRAY_SIZE(invalid_sequences);
+
+	entry = self_id_sequence_enumerator_next(&enumerator, &count);
+	KUNIT_EXPECT_EQ(test, PTR_ERR(entry), -EPROTO);
+}
+
+static void test_self_id_sequence_get_port_status(struct kunit *test)
+{
+	static const u32 expected[] = {
+		0x000000e5,
+		0x00839e79,
+		0x0091e79d,
+		0x00a279e4,
+	};
+	u32 quadlets [] = {
+		0x00000001,
+		0x00800001,
+		0x00900001,
+		0x00a00000,
+	};
+	enum phy_packet_self_id_port_status port_status[28];
+	unsigned int port_capacity;
+	unsigned int port_index;
+
+	KUNIT_ASSERT_EQ(test, ARRAY_SIZE(expected), ARRAY_SIZE(quadlets));
+
+	// With an extra port.
+	port_capacity = self_id_sequence_get_port_capacity(ARRAY_SIZE(expected)) + 1;
+	KUNIT_ASSERT_EQ(test, port_capacity, ARRAY_SIZE(port_status));
+
+	for (port_index = 0; port_index < port_capacity; ++port_index) {
+		port_status[port_index] =
+			self_id_sequence_get_port_status(expected, ARRAY_SIZE(expected), port_index);
+		self_id_sequence_set_port_status(quadlets, ARRAY_SIZE(quadlets), port_index,
+						 port_status[port_index]);
+	}
+
+	// Self ID zero.
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[0]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[1]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[2]);
+
+	// Self ID one.
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[3]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[4]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[5]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[6]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[7]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[8]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[9]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[10]);
+
+	// Self ID two.
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[11]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[12]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[13]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[14]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[15]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[16]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[17]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[18]);
+
+	// Self ID three.
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[19]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[20]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[21]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[22]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[23]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_CHILD, port_status[24]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_PARENT, port_status[25]);
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NCONN, port_status[26]);
+
+	// Our of order.
+	KUNIT_EXPECT_EQ(test, PHY_PACKET_SELF_ID_PORT_STATUS_NONE, port_status[27]);
+
+	KUNIT_EXPECT_MEMEQ(test, quadlets, expected, sizeof(expected));
+}
+
+static struct kunit_case self_id_sequence_helper_test_cases[] = {
+	KUNIT_CASE(test_self_id_sequence_enumerator_valid),
+	KUNIT_CASE(test_self_id_sequence_enumerator_invalid),
+	KUNIT_CASE(test_self_id_sequence_get_port_status),
+	{}
+};
+
+static struct kunit_suite self_id_sequence_helper_test_suite = {
+	.name = "self-id-sequence-helper",
+	.test_cases = self_id_sequence_helper_test_cases,
+};
+kunit_test_suite(self_id_sequence_helper_test_suite);
+
+MODULE_DESCRIPTION("Unit test suite for helpers of self ID sequence");
+MODULE_LICENSE("GPL");