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, 91 insertions, 0 deletions

diff --git a/drivers/input/serio/i8042.h b/drivers/input/serio/i8042.h
new file mode 100644
index 000000000..5f61672d5
--- /dev/null
+++ b/drivers/input/serio/i8042.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _I8042_H
+#define _I8042_H
+
+
+/*
+ *  Copyright (c) 1999-2002 Vojtech Pavlik
+ */
+
+/*
+ * Arch-dependent inline functions and defines.
+ */
+
+#if defined(CONFIG_MACH_JAZZ)
+#include "i8042-jazzio.h"
+#elif defined(CONFIG_SGI_HAS_I8042)
+#include "i8042-ip22io.h"
+#elif defined(CONFIG_SNI_RM)
+#include "i8042-snirm.h"
+#elif defined(CONFIG_SPARC)
+#include "i8042-sparcio.h"
+#elif defined(CONFIG_X86) || defined(CONFIG_LOONGARCH)
+#include "i8042-acpipnpio.h"
+#else
+#include "i8042-io.h"
+#endif
+
+/*
+ * This is in 50us units, the time we wait for the i8042 to react. This
+ * has to be long enough for the i8042 itself to timeout on sending a byte
+ * to a non-existent mouse.
+ */
+
+#define I8042_CTL_TIMEOUT	10000
+
+/*
+ * Return codes.
+ */
+
+#define I8042_RET_CTL_TEST	0x55
+
+/*
+ * Expected maximum internal i8042 buffer size. This is used for flushing
+ * the i8042 buffers.
+ */
+
+#define I8042_BUFFER_SIZE	16
+
+/*
+ * Number of AUX ports on controllers supporting active multiplexing
+ * specification
+ */
+
+#define I8042_NUM_MUX_PORTS	4
+
+/*
+ * Debug.
+ */
+
+#ifdef DEBUG
+static unsigned long i8042_start_time;
+#define dbg_init() do { i8042_start_time = jiffies; } while (0)
+#define dbg(format, arg...)							\
+	do {									\
+		if (i8042_debug)						\
+			printk(KERN_DEBUG KBUILD_MODNAME ": [%d] " format,	\
+			       (int) (jiffies - i8042_start_time), ##arg);	\
+	} while (0)
+
+#define filter_dbg(filter, data, format, args...)		\
+	do {							\
+		if (!i8042_debug)				\
+			break;					\
+								\
+		if (!filter || i8042_unmask_kbd_data)		\
+			dbg("%02x " format, data, ##args);	\
+		else						\
+			dbg("** " format, ##args);		\
+	} while (0)
+#else
+#define dbg_init() do { } while (0)
+#define dbg(format, arg...)							\
+	do {									\
+		if (0)								\
+			printk(KERN_DEBUG pr_fmt(format), ##arg);		\
+	} while (0)
+
+#define filter_dbg(filter, data, format, args...) do { } while (0)
+#endif
+
+#endif /* _I8042_H */