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, 57 insertions, 0 deletions

diff --git a/drivers/bcma/scan.h b/drivers/bcma/scan.h
new file mode 100644
index 000000000..e53079a3d
--- /dev/null
+++ b/drivers/bcma/scan.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BCMA_SCAN_H_
+#define BCMA_SCAN_H_
+
+#define BCMA_ADDR_BASE		0x18000000
+#define BCMA_WRAP_BASE		0x18100000
+
+#define SCAN_ER_VALID		0x00000001
+#define SCAN_ER_TAGX		0x00000006 /* we have to ignore 0x8 bit when checking tag for SCAN_ER_TAG_ADDR */
+#define SCAN_ER_TAG		0x0000000E
+#define  SCAN_ER_TAG_CI		0x00000000
+#define  SCAN_ER_TAG_MP		0x00000002
+#define  SCAN_ER_TAG_ADDR	0x00000004
+#define  SCAN_ER_TAG_END	0x0000000E
+#define SCAN_ER_BAD		0xFFFFFFFF
+
+#define SCAN_CIA_CLASS		0x000000F0
+#define SCAN_CIA_CLASS_SHIFT	4
+#define SCAN_CIA_ID		0x000FFF00
+#define SCAN_CIA_ID_SHIFT	8
+#define SCAN_CIA_MANUF		0xFFF00000
+#define SCAN_CIA_MANUF_SHIFT	20
+
+#define SCAN_CIB_NMP		0x000001F0
+#define SCAN_CIB_NMP_SHIFT	4
+#define SCAN_CIB_NSP		0x00003E00
+#define SCAN_CIB_NSP_SHIFT	9
+#define SCAN_CIB_NMW		0x0007C000
+#define SCAN_CIB_NMW_SHIFT	14
+#define SCAN_CIB_NSW		0x00F80000
+#define SCAN_CIB_NSW_SHIFT	19
+#define SCAN_CIB_REV		0xFF000000
+#define SCAN_CIB_REV_SHIFT	24
+
+#define SCAN_ADDR_AG32		0x00000008
+#define SCAN_ADDR_SZ		0x00000030
+#define SCAN_ADDR_SZ_SHIFT	4
+#define  SCAN_ADDR_SZ_4K	0x00000000
+#define  SCAN_ADDR_SZ_8K	0x00000010
+#define  SCAN_ADDR_SZ_16K	0x00000020
+#define  SCAN_ADDR_SZ_SZD	0x00000030
+#define SCAN_ADDR_TYPE		0x000000C0
+#define  SCAN_ADDR_TYPE_SLAVE	0x00000000
+#define  SCAN_ADDR_TYPE_BRIDGE	0x00000040
+#define  SCAN_ADDR_TYPE_SWRAP	0x00000080
+#define  SCAN_ADDR_TYPE_MWRAP	0x000000C0
+#define SCAN_ADDR_PORT		0x00000F00
+#define SCAN_ADDR_PORT_SHIFT	8
+#define SCAN_ADDR_ADDR		0xFFFFF000
+
+#define SCAN_ADDR_SZ_BASE	0x00001000	/* 4KB */
+
+#define SCAN_SIZE_SZ_ALIGN	0x00000FFF
+#define SCAN_SIZE_SZ		0xFFFFF000
+#define SCAN_SIZE_SG32		0x00000008
+
+#endif /* BCMA_SCAN_H_ */