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, 53 insertions, 0 deletions

diff --git a/drivers/nfc/mei_phy.h b/drivers/nfc/mei_phy.h
new file mode 100644
index 000000000..9b9c5eb54
--- /dev/null
+++ b/drivers/nfc/mei_phy.h
@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LOCAL_MEI_PHY_H_
+#define __LOCAL_MEI_PHY_H_
+
+#include <linux/mei_cl_bus.h>
+#include <net/nfc/hci.h>
+#include <linux/uuid.h>
+
+#define MEI_NFC_UUID UUID_LE(0x0bb17a78, 0x2a8e, 0x4c50, \
+		0x94, 0xd4, 0x50, 0x26, 0x67, 0x23, 0x77, 0x5c)
+#define MEI_NFC_HEADER_SIZE 10
+#define MEI_NFC_MAX_HCI_PAYLOAD 300
+
+/**
+ * struct nfc_mei_phy - NFC description of the MEI PHY and interface functions
+ *
+ * @cldev: mei client device
+ * @hdev:   nfc hci device
+ *
+ * @send_wq: send completion wait queue
+ * @fw_ivn: NFC Interface Version Number
+ * @vendor_id: NFC manufacturer ID
+ * @radio_type: NFC radio type
+ * @reserved: reserved for alignment
+ * @req_id:  message counter
+ * @recv_req_id: reception message counter
+ * @powered: the device is in powered state
+ * @hard_fault: < 0 if hardware error occurred
+ *    and prevents normal operation.
+ */
+struct nfc_mei_phy {
+	struct mei_cl_device *cldev;
+	struct nfc_hci_dev *hdev;
+
+	wait_queue_head_t send_wq;
+	u8 fw_ivn;
+	u8 vendor_id;
+	u8 radio_type;
+	u8 reserved;
+
+	u16 req_id;
+	u16 recv_req_id;
+
+	int powered;
+	int hard_fault;
+};
+
+extern const struct nfc_phy_ops mei_phy_ops;
+
+struct nfc_mei_phy *nfc_mei_phy_alloc(struct mei_cl_device *device);
+void nfc_mei_phy_free(struct nfc_mei_phy *phy);
+
+#endif /* __LOCAL_MEI_PHY_H_ */