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, 128 insertions, 0 deletions

diff --git a/arch/sh/lib/ashiftrt.S b/arch/sh/lib/ashiftrt.S
new file mode 100644
index 000000000..0f7145e3c
--- /dev/null
+++ b/arch/sh/lib/ashiftrt.S
@@ -0,0 +1,128 @@
+/* SPDX-License-Identifier: GPL-2.0+ WITH GCC-exception-2.0
+
+   Copyright (C) 1994, 1995, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
+   2004, 2005, 2006
+   Free Software Foundation, Inc.
+*/
+
+!! libgcc routines for the Renesas / SuperH SH CPUs.
+!! Contributed by Steve Chamberlain.
+!! sac@cygnus.com
+
+!! ashiftrt_r4_x, ___ashrsi3, ___ashlsi3, ___lshrsi3 routines
+!! recoded in assembly by Toshiyasu Morita
+!! tm@netcom.com
+
+/* SH2 optimizations for ___ashrsi3, ___ashlsi3, ___lshrsi3 and
+   ELF local label prefixes by J"orn Rennecke
+   amylaar@cygnus.com  */
+
+	.global	__ashiftrt_r4_0
+	.global	__ashiftrt_r4_1
+	.global	__ashiftrt_r4_2
+	.global	__ashiftrt_r4_3
+	.global	__ashiftrt_r4_4
+	.global	__ashiftrt_r4_5
+	.global	__ashiftrt_r4_6
+	.global	__ashiftrt_r4_7
+	.global	__ashiftrt_r4_8
+	.global	__ashiftrt_r4_9
+	.global	__ashiftrt_r4_10
+	.global	__ashiftrt_r4_11
+	.global	__ashiftrt_r4_12
+	.global	__ashiftrt_r4_13
+	.global	__ashiftrt_r4_14
+	.global	__ashiftrt_r4_15
+	.global	__ashiftrt_r4_16
+	.global	__ashiftrt_r4_17
+	.global	__ashiftrt_r4_18
+	.global	__ashiftrt_r4_19
+	.global	__ashiftrt_r4_20
+	.global	__ashiftrt_r4_21
+	.global	__ashiftrt_r4_22
+	.global	__ashiftrt_r4_23
+	.global	__ashiftrt_r4_24
+	.global	__ashiftrt_r4_25
+	.global	__ashiftrt_r4_26
+	.global	__ashiftrt_r4_27
+	.global	__ashiftrt_r4_28
+	.global	__ashiftrt_r4_29
+	.global	__ashiftrt_r4_30
+	.global	__ashiftrt_r4_31
+	.global	__ashiftrt_r4_32
+
+	.align	1
+__ashiftrt_r4_32:
+__ashiftrt_r4_31:
+	rotcl	r4
+	rts
+	subc	r4,r4
+__ashiftrt_r4_30:
+	shar	r4
+__ashiftrt_r4_29:
+	shar	r4
+__ashiftrt_r4_28:
+	shar	r4
+__ashiftrt_r4_27:
+	shar	r4
+__ashiftrt_r4_26:
+	shar	r4
+__ashiftrt_r4_25:
+	shar	r4
+__ashiftrt_r4_24:
+	shlr16	r4
+	shlr8	r4
+	rts
+	exts.b	r4,r4
+__ashiftrt_r4_23:
+	shar	r4
+__ashiftrt_r4_22:
+	shar	r4
+__ashiftrt_r4_21:
+	shar	r4
+__ashiftrt_r4_20:
+	shar	r4
+__ashiftrt_r4_19:
+	shar	r4
+__ashiftrt_r4_18:
+	shar	r4
+__ashiftrt_r4_17:
+	shar	r4
+__ashiftrt_r4_16:
+	shlr16	r4
+	rts
+	exts.w	r4,r4
+__ashiftrt_r4_15:
+	shar	r4
+__ashiftrt_r4_14:
+	shar	r4
+__ashiftrt_r4_13:
+	shar	r4
+__ashiftrt_r4_12:
+	shar	r4
+__ashiftrt_r4_11:
+	shar	r4
+__ashiftrt_r4_10:
+	shar	r4
+__ashiftrt_r4_9:
+	shar	r4
+__ashiftrt_r4_8:
+	shar	r4
+__ashiftrt_r4_7:
+	shar	r4
+__ashiftrt_r4_6:
+	shar	r4
+__ashiftrt_r4_5:
+	shar	r4
+__ashiftrt_r4_4:
+	shar	r4
+__ashiftrt_r4_3:
+	shar	r4
+__ashiftrt_r4_2:
+	shar	r4
+__ashiftrt_r4_1:
+	rts
+	shar	r4
+__ashiftrt_r4_0:
+	rts
+	nop