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, 179 insertions, 0 deletions

diff --git a/arch/sh/lib/ashrsi3.S b/arch/sh/lib/ashrsi3.S
new file mode 100644
index 000000000..bf3c4e03e
--- /dev/null
+++ b/arch/sh/lib/ashrsi3.S
@@ -0,0 +1,179 @@
+/* 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  */
+
+!
+! __ashrsi3
+!
+! Entry:
+!
+! r4: Value to shift
+! r5: Shifts
+!
+! Exit:
+!
+! r0: Result
+!
+! Destroys:
+!
+! (none)
+!
+! __ashrsi3_r0
+!
+! Entry:
+!
+! r4: Value to shift
+! r0: Shifts
+!
+! Exit:
+!
+! r0: Result
+!
+! Destroys:
+!
+! (none)
+
+	.global	__ashrsi3
+	.global	__ashrsi3_r0
+	
+	.align	2
+__ashrsi3:
+	mov	r5,r0
+	.align	2
+__ashrsi3_r0:
+	and	#31,r0
+	mov.l	r4,@-r15
+	mov	r0,r4
+	mova	ashrsi3_table,r0
+	mov.b	@(r0,r4),r4
+	add	r4,r0
+	jmp	@r0
+	mov.l	@r15+,r0
+
+	.align	2
+ashrsi3_table:
+	.byte		ashrsi3_0-ashrsi3_table
+	.byte		ashrsi3_1-ashrsi3_table
+	.byte		ashrsi3_2-ashrsi3_table
+	.byte		ashrsi3_3-ashrsi3_table
+	.byte		ashrsi3_4-ashrsi3_table
+	.byte		ashrsi3_5-ashrsi3_table
+	.byte		ashrsi3_6-ashrsi3_table
+	.byte		ashrsi3_7-ashrsi3_table
+	.byte		ashrsi3_8-ashrsi3_table
+	.byte		ashrsi3_9-ashrsi3_table
+	.byte		ashrsi3_10-ashrsi3_table
+	.byte		ashrsi3_11-ashrsi3_table
+	.byte		ashrsi3_12-ashrsi3_table
+	.byte		ashrsi3_13-ashrsi3_table
+	.byte		ashrsi3_14-ashrsi3_table
+	.byte		ashrsi3_15-ashrsi3_table
+	.byte		ashrsi3_16-ashrsi3_table
+	.byte		ashrsi3_17-ashrsi3_table
+	.byte		ashrsi3_18-ashrsi3_table
+	.byte		ashrsi3_19-ashrsi3_table
+	.byte		ashrsi3_20-ashrsi3_table
+	.byte		ashrsi3_21-ashrsi3_table
+	.byte		ashrsi3_22-ashrsi3_table
+	.byte		ashrsi3_23-ashrsi3_table
+	.byte		ashrsi3_24-ashrsi3_table
+	.byte		ashrsi3_25-ashrsi3_table
+	.byte		ashrsi3_26-ashrsi3_table
+	.byte		ashrsi3_27-ashrsi3_table
+	.byte		ashrsi3_28-ashrsi3_table
+	.byte		ashrsi3_29-ashrsi3_table
+	.byte		ashrsi3_30-ashrsi3_table
+	.byte		ashrsi3_31-ashrsi3_table
+
+ashrsi3_31:
+	rotcl	r0
+	rts
+	subc	r0,r0
+
+ashrsi3_30:
+	shar	r0
+ashrsi3_29:
+	shar	r0
+ashrsi3_28:
+	shar	r0
+ashrsi3_27:
+	shar	r0
+ashrsi3_26:
+	shar	r0
+ashrsi3_25:
+	shar	r0
+ashrsi3_24:
+	shlr16	r0
+	shlr8	r0
+	rts
+	exts.b	r0,r0
+
+ashrsi3_23:
+	shar	r0
+ashrsi3_22:
+	shar	r0
+ashrsi3_21:
+	shar	r0
+ashrsi3_20:
+	shar	r0
+ashrsi3_19:
+	shar	r0
+ashrsi3_18:
+	shar	r0
+ashrsi3_17:
+	shar	r0
+ashrsi3_16:
+	shlr16	r0
+	rts
+	exts.w	r0,r0
+
+ashrsi3_15:
+	shar	r0
+ashrsi3_14:
+	shar	r0
+ashrsi3_13:
+	shar	r0
+ashrsi3_12:
+	shar	r0
+ashrsi3_11:
+	shar	r0
+ashrsi3_10:
+	shar	r0
+ashrsi3_9:
+	shar	r0
+ashrsi3_8:
+	shar	r0
+ashrsi3_7:
+	shar	r0
+ashrsi3_6:
+	shar	r0
+ashrsi3_5:
+	shar	r0
+ashrsi3_4:
+	shar	r0
+ashrsi3_3:
+	shar	r0
+ashrsi3_2:
+	shar	r0
+ashrsi3_1:
+	rts
+	shar	r0
+
+ashrsi3_0:
+	rts
+	nop