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, 87 insertions, 0 deletions

diff --git a/arch/m68k/coldfire/firebee.c b/arch/m68k/coldfire/firebee.c
new file mode 100644
index 000000000..3b9d4fc6f
--- /dev/null
+++ b/arch/m68k/coldfire/firebee.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+/***************************************************************************/
+
+/*
+ *	firebee.c -- extra startup code support for the FireBee boards
+ *
+ *	Copyright (C) 2011, Greg Ungerer (gerg@snapgear.com)
+ */
+
+/***************************************************************************/
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mtd/physmap.h>
+#include <asm/coldfire.h>
+#include <asm/mcfsim.h>
+
+/***************************************************************************/
+
+/*
+ *	8MB of NOR flash fitted to the FireBee board.
+ */
+#define	FLASH_PHYS_ADDR		0xe0000000	/* Physical address of flash */
+#define	FLASH_PHYS_SIZE		0x00800000	/* Size of flash */
+
+#define	PART_BOOT_START		0x00000000	/* Start at bottom of flash */
+#define	PART_BOOT_SIZE		0x00040000	/* 256k in size */
+#define	PART_IMAGE_START	0x00040000	/* Start after boot loader */
+#define	PART_IMAGE_SIZE		0x006c0000	/* Most of flash */
+#define	PART_FPGA_START		0x00700000	/* Start at offset 7MB */
+#define	PART_FPGA_SIZE		0x00100000	/* 1MB in size */
+
+static struct mtd_partition firebee_flash_parts[] = {
+	{
+		.name	= "dBUG",
+		.offset	= PART_BOOT_START,
+		.size	= PART_BOOT_SIZE,
+	},
+	{
+		.name	= "FPGA",
+		.offset	= PART_FPGA_START,
+		.size	= PART_FPGA_SIZE,
+	},
+	{
+		.name	= "image",
+		.offset	= PART_IMAGE_START,
+		.size	= PART_IMAGE_SIZE,
+	},
+};
+
+static struct physmap_flash_data firebee_flash_data = {
+	.width		= 2,
+	.nr_parts	= ARRAY_SIZE(firebee_flash_parts),
+	.parts		= firebee_flash_parts,
+};
+
+static struct resource firebee_flash_resource = {
+	.start		= FLASH_PHYS_ADDR,
+	.end		= FLASH_PHYS_ADDR + FLASH_PHYS_SIZE,
+	.flags		= IORESOURCE_MEM,
+};
+
+static struct platform_device firebee_flash = {
+	.name		= "physmap-flash",
+	.id		= 0,
+	.dev		= {
+		.platform_data = &firebee_flash_data,
+	},
+	.num_resources	= 1,
+	.resource	= &firebee_flash_resource,
+};
+
+/***************************************************************************/
+
+static int __init init_firebee(void)
+{
+	platform_device_register(&firebee_flash);
+	return 0;
+}
+
+arch_initcall(init_firebee);
+
+/***************************************************************************/