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, 232 insertions, 0 deletions

diff --git a/drivers/input/keyboard/atakbd.c b/drivers/input/keyboard/atakbd.c
new file mode 100644
index 000000000..07e17e563
--- /dev/null
+++ b/drivers/input/keyboard/atakbd.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  atakbd.c
+ *
+ *  Copyright (c) 2005 Michael Schmitz
+ *
+ * Based on amikbd.c, which is
+ *
+ *  Copyright (c) 2000-2001 Vojtech Pavlik
+ *
+ *  Based on the work of:
+ *	Hamish Macdonald
+ */
+
+/*
+ * Atari keyboard driver for Linux/m68k
+ *
+ * The low level init and interrupt stuff is handled in arch/mm68k/atari/atakeyb.c
+ * (the keyboard ACIA also handles the mouse and joystick data, and the keyboard
+ * interrupt is shared with the MIDI ACIA so MIDI data also get handled there).
+ * This driver only deals with handing key events off to the input layer.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+
+#include <asm/atariints.h>
+#include <asm/atarihw.h>
+#include <asm/atarikb.h>
+#include <asm/irq.h>
+
+MODULE_AUTHOR("Michael Schmitz <schmitz@biophys.uni-duesseldorf.de>");
+MODULE_DESCRIPTION("Atari keyboard driver");
+MODULE_LICENSE("GPL");
+
+/*
+ 0x47: KP_7     71
+ 0x48: KP_8     72
+ 0x49: KP_9     73
+ 0x62: KP_/     98
+ 0x4b: KP_4     75
+ 0x4c: KP_5     76
+ 0x4d: KP_6     77
+ 0x37: KP_*     55
+ 0x4f: KP_1     79
+ 0x50: KP_2     80
+ 0x51: KP_3     81
+ 0x4a: KP_-     74
+ 0x52: KP_0     82
+ 0x53: KP_.     83
+ 0x4e: KP_+     78
+
+ 0x67: Up       103
+ 0x6c: Down     108
+ 0x69: Left     105
+ 0x6a: Right    106
+ */
+
+
+static unsigned char atakbd_keycode[0x73] = {	/* American layout */
+	[1]	 = KEY_ESC,
+	[2]	 = KEY_1,
+	[3]	 = KEY_2,
+	[4]	 = KEY_3,
+	[5]	 = KEY_4,
+	[6]	 = KEY_5,
+	[7]	 = KEY_6,
+	[8]	 = KEY_7,
+	[9]	 = KEY_8,
+	[10]	 = KEY_9,
+	[11]	 = KEY_0,
+	[12]	 = KEY_MINUS,
+	[13]	 = KEY_EQUAL,
+	[14]	 = KEY_BACKSPACE,
+	[15]	 = KEY_TAB,
+	[16]	 = KEY_Q,
+	[17]	 = KEY_W,
+	[18]	 = KEY_E,
+	[19]	 = KEY_R,
+	[20]	 = KEY_T,
+	[21]	 = KEY_Y,
+	[22]	 = KEY_U,
+	[23]	 = KEY_I,
+	[24]	 = KEY_O,
+	[25]	 = KEY_P,
+	[26]	 = KEY_LEFTBRACE,
+	[27]	 = KEY_RIGHTBRACE,
+	[28]	 = KEY_ENTER,
+	[29]	 = KEY_LEFTCTRL,
+	[30]	 = KEY_A,
+	[31]	 = KEY_S,
+	[32]	 = KEY_D,
+	[33]	 = KEY_F,
+	[34]	 = KEY_G,
+	[35]	 = KEY_H,
+	[36]	 = KEY_J,
+	[37]	 = KEY_K,
+	[38]	 = KEY_L,
+	[39]	 = KEY_SEMICOLON,
+	[40]	 = KEY_APOSTROPHE,
+	[41]	 = KEY_GRAVE,
+	[42]	 = KEY_LEFTSHIFT,
+	[43]	 = KEY_BACKSLASH,
+	[44]	 = KEY_Z,
+	[45]	 = KEY_X,
+	[46]	 = KEY_C,
+	[47]	 = KEY_V,
+	[48]	 = KEY_B,
+	[49]	 = KEY_N,
+	[50]	 = KEY_M,
+	[51]	 = KEY_COMMA,
+	[52]	 = KEY_DOT,
+	[53]	 = KEY_SLASH,
+	[54]	 = KEY_RIGHTSHIFT,
+	[55]	 = KEY_KPASTERISK,
+	[56]	 = KEY_LEFTALT,
+	[57]	 = KEY_SPACE,
+	[58]	 = KEY_CAPSLOCK,
+	[59]	 = KEY_F1,
+	[60]	 = KEY_F2,
+	[61]	 = KEY_F3,
+	[62]	 = KEY_F4,
+	[63]	 = KEY_F5,
+	[64]	 = KEY_F6,
+	[65]	 = KEY_F7,
+	[66]	 = KEY_F8,
+	[67]	 = KEY_F9,
+	[68]	 = KEY_F10,
+	[71]	 = KEY_HOME,
+	[72]	 = KEY_UP,
+	[74]	 = KEY_KPMINUS,
+	[75]	 = KEY_LEFT,
+	[77]	 = KEY_RIGHT,
+	[78]	 = KEY_KPPLUS,
+	[80]	 = KEY_DOWN,
+	[82]	 = KEY_INSERT,
+	[83]	 = KEY_DELETE,
+	[96]	 = KEY_102ND,
+	[97]	 = KEY_UNDO,
+	[98]	 = KEY_HELP,
+	[99]	 = KEY_KPLEFTPAREN,
+	[100]	 = KEY_KPRIGHTPAREN,
+	[101]	 = KEY_KPSLASH,
+	[102]	 = KEY_KPASTERISK,
+	[103]	 = KEY_KP7,
+	[104]	 = KEY_KP8,
+	[105]	 = KEY_KP9,
+	[106]	 = KEY_KP4,
+	[107]	 = KEY_KP5,
+	[108]	 = KEY_KP6,
+	[109]	 = KEY_KP1,
+	[110]	 = KEY_KP2,
+	[111]	 = KEY_KP3,
+	[112]	 = KEY_KP0,
+	[113]	 = KEY_KPDOT,
+	[114]	 = KEY_KPENTER,
+};
+
+static struct input_dev *atakbd_dev;
+
+static void atakbd_interrupt(unsigned char scancode, char down)
+{
+
+	if (scancode < 0x73) {		/* scancodes < 0xf3 are keys */
+
+		// report raw events here?
+
+		scancode = atakbd_keycode[scancode];
+
+		input_report_key(atakbd_dev, scancode, down);
+		input_sync(atakbd_dev);
+	} else				/* scancodes >= 0xf3 are mouse data, most likely */
+		printk(KERN_INFO "atakbd: unhandled scancode %x\n", scancode);
+
+	return;
+}
+
+static int __init atakbd_init(void)
+{
+	int i, error;
+
+	if (!MACH_IS_ATARI || !ATARIHW_PRESENT(ST_MFP))
+		return -ENODEV;
+
+	// need to init core driver if not already done so
+	error = atari_keyb_init();
+	if (error)
+		return error;
+
+	atakbd_dev = input_allocate_device();
+	if (!atakbd_dev)
+		return -ENOMEM;
+
+	atakbd_dev->name = "Atari Keyboard";
+	atakbd_dev->phys = "atakbd/input0";
+	atakbd_dev->id.bustype = BUS_HOST;
+	atakbd_dev->id.vendor = 0x0001;
+	atakbd_dev->id.product = 0x0001;
+	atakbd_dev->id.version = 0x0100;
+
+	atakbd_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
+	atakbd_dev->keycode = atakbd_keycode;
+	atakbd_dev->keycodesize = sizeof(unsigned char);
+	atakbd_dev->keycodemax = ARRAY_SIZE(atakbd_keycode);
+
+	for (i = 1; i < 0x72; i++) {
+		set_bit(atakbd_keycode[i], atakbd_dev->keybit);
+	}
+
+	/* error check */
+	error = input_register_device(atakbd_dev);
+	if (error) {
+		input_free_device(atakbd_dev);
+		return error;
+	}
+
+	atari_input_keyboard_interrupt_hook = atakbd_interrupt;
+
+	return 0;
+}
+
+static void __exit atakbd_exit(void)
+{
+	atari_input_keyboard_interrupt_hook = NULL;
+	input_unregister_device(atakbd_dev);
+}
+
+module_init(atakbd_init);
+module_exit(atakbd_exit);