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, 63 insertions, 0 deletions

diff --git a/drivers/greybus/arpc.h b/drivers/greybus/arpc.h
new file mode 100644
index 000000000..b9ea81b55
--- /dev/null
+++ b/drivers/greybus/arpc.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
+/*
+ * Copyright(c) 2016 Google Inc. All rights reserved.
+ * Copyright(c) 2016 Linaro Ltd. All rights reserved.
+ */
+
+#ifndef __ARPC_H
+#define __ARPC_H
+
+/* APBridgeA RPC (ARPC) */
+
+enum arpc_result {
+	ARPC_SUCCESS		= 0x00,
+	ARPC_NO_MEMORY		= 0x01,
+	ARPC_INVALID		= 0x02,
+	ARPC_TIMEOUT		= 0x03,
+	ARPC_UNKNOWN_ERROR	= 0xff,
+};
+
+struct arpc_request_message {
+	__le16	id;		/* RPC unique id */
+	__le16	size;		/* Size in bytes of header + payload */
+	__u8	type;		/* RPC type */
+	__u8	data[];	/* ARPC data */
+} __packed;
+
+struct arpc_response_message {
+	__le16	id;		/* RPC unique id */
+	__u8	result;		/* Result of RPC */
+} __packed;
+
+/* ARPC requests */
+#define ARPC_TYPE_CPORT_CONNECTED		0x01
+#define ARPC_TYPE_CPORT_QUIESCE			0x02
+#define ARPC_TYPE_CPORT_CLEAR			0x03
+#define ARPC_TYPE_CPORT_FLUSH			0x04
+#define ARPC_TYPE_CPORT_SHUTDOWN		0x05
+
+struct arpc_cport_connected_req {
+	__le16 cport_id;
+} __packed;
+
+struct arpc_cport_quiesce_req {
+	__le16 cport_id;
+	__le16 peer_space;
+	__le16 timeout;
+} __packed;
+
+struct arpc_cport_clear_req {
+	__le16 cport_id;
+} __packed;
+
+struct arpc_cport_flush_req {
+	__le16 cport_id;
+} __packed;
+
+struct arpc_cport_shutdown_req {
+	__le16 cport_id;
+	__le16 timeout;
+	__u8 phase;
+} __packed;
+
+#endif	/* __ARPC_H */