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, 49 insertions, 0 deletions

diff --git a/include/sound/sof/xtensa.h b/include/sound/sof/xtensa.h
new file mode 100644
index 000000000..ef70f8e26
--- /dev/null
+++ b/include/sound/sof/xtensa.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */
+/*
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * Copyright(c) 2018 Intel Corporation
+ */
+
+#ifndef __INCLUDE_SOUND_SOF_XTENSA_H__
+#define __INCLUDE_SOUND_SOF_XTENSA_H__
+
+#include <sound/sof/header.h>
+
+/*
+ * Architecture specific debug
+ */
+
+/* Xtensa Firmware Oops data */
+struct sof_ipc_dsp_oops_xtensa {
+	struct sof_ipc_dsp_oops_arch_hdr arch_hdr;
+	struct sof_ipc_dsp_oops_plat_hdr plat_hdr;
+	uint32_t exccause;
+	uint32_t excvaddr;
+	uint32_t ps;
+	uint32_t epc1;
+	uint32_t epc2;
+	uint32_t epc3;
+	uint32_t epc4;
+	uint32_t epc5;
+	uint32_t epc6;
+	uint32_t epc7;
+	uint32_t eps2;
+	uint32_t eps3;
+	uint32_t eps4;
+	uint32_t eps5;
+	uint32_t eps6;
+	uint32_t eps7;
+	uint32_t depc;
+	uint32_t intenable;
+	uint32_t interrupt;
+	uint32_t sar;
+	uint32_t debugcause;
+	uint32_t windowbase;
+	uint32_t windowstart;
+	uint32_t excsave1;
+	uint32_t ar[];
+}  __packed;
+
+#endif