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, 244 insertions, 0 deletions

diff --git a/drivers/input/joystick/cobra.c b/drivers/input/joystick/cobra.c
new file mode 100644
index 000000000..ffa6d49c8
--- /dev/null
+++ b/drivers/input/joystick/cobra.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 1999-2001 Vojtech Pavlik
+ */
+
+/*
+ * Creative Labs Blaster GamePad Cobra driver for Linux
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/gameport.h>
+#include <linux/input.h>
+#include <linux/jiffies.h>
+
+#define DRIVER_DESC	"Creative Labs Blaster GamePad Cobra driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define COBRA_MAX_STROBE	45	/* 45 us max wait for first strobe */
+#define COBRA_LENGTH		36
+
+static int cobra_btn[] = { BTN_START, BTN_SELECT, BTN_TL, BTN_TR, BTN_X, BTN_Y, BTN_Z, BTN_A, BTN_B, BTN_C, BTN_TL2, BTN_TR2, 0 };
+
+struct cobra {
+	struct gameport *gameport;
+	struct input_dev *dev[2];
+	int reads;
+	int bads;
+	unsigned char exists;
+	char phys[2][32];
+};
+
+static unsigned char cobra_read_packet(struct gameport *gameport, unsigned int *data)
+{
+	unsigned long flags;
+	unsigned char u, v, w;
+	__u64 buf[2];
+	int r[2], t[2];
+	int i, j, ret;
+
+	int strobe = gameport_time(gameport, COBRA_MAX_STROBE);
+
+	for (i = 0; i < 2; i++) {
+		r[i] = buf[i] = 0;
+		t[i] = COBRA_MAX_STROBE;
+	}
+
+	local_irq_save(flags);
+
+	u = gameport_read(gameport);
+
+	do {
+		t[0]--; t[1]--;
+		v = gameport_read(gameport);
+		for (i = 0, w = u ^ v; i < 2 && w; i++, w >>= 2)
+			if (w & 0x30) {
+				if ((w & 0x30) < 0x30 && r[i] < COBRA_LENGTH && t[i] > 0) {
+					buf[i] |= (__u64)((w >> 5) & 1) << r[i]++;
+					t[i] = strobe;
+					u = v;
+				} else t[i] = 0;
+			}
+	} while (t[0] > 0 || t[1] > 0);
+
+	local_irq_restore(flags);
+
+	ret = 0;
+
+	for (i = 0; i < 2; i++) {
+
+		if (r[i] != COBRA_LENGTH) continue;
+
+		for (j = 0; j < COBRA_LENGTH && (buf[i] & 0x04104107f) ^ 0x041041040; j++)
+			buf[i] = (buf[i] >> 1) | ((__u64)(buf[i] & 1) << (COBRA_LENGTH - 1));
+
+		if (j < COBRA_LENGTH) ret |= (1 << i);
+
+		data[i] = ((buf[i] >>  7) & 0x000001f) | ((buf[i] >>  8) & 0x00003e0)
+			| ((buf[i] >>  9) & 0x0007c00) | ((buf[i] >> 10) & 0x00f8000)
+			| ((buf[i] >> 11) & 0x1f00000);
+
+	}
+
+	return ret;
+}
+
+static void cobra_poll(struct gameport *gameport)
+{
+	struct cobra *cobra = gameport_get_drvdata(gameport);
+	struct input_dev *dev;
+	unsigned int data[2];
+	int i, j, r;
+
+	cobra->reads++;
+
+	if ((r = cobra_read_packet(gameport, data)) != cobra->exists) {
+		cobra->bads++;
+		return;
+	}
+
+	for (i = 0; i < 2; i++)
+		if (cobra->exists & r & (1 << i)) {
+
+			dev = cobra->dev[i];
+
+			input_report_abs(dev, ABS_X, ((data[i] >> 4) & 1) - ((data[i] >> 3) & 1));
+			input_report_abs(dev, ABS_Y, ((data[i] >> 2) & 1) - ((data[i] >> 1) & 1));
+
+			for (j = 0; cobra_btn[j]; j++)
+				input_report_key(dev, cobra_btn[j], data[i] & (0x20 << j));
+
+			input_sync(dev);
+
+		}
+}
+
+static int cobra_open(struct input_dev *dev)
+{
+	struct cobra *cobra = input_get_drvdata(dev);
+
+	gameport_start_polling(cobra->gameport);
+	return 0;
+}
+
+static void cobra_close(struct input_dev *dev)
+{
+	struct cobra *cobra = input_get_drvdata(dev);
+
+	gameport_stop_polling(cobra->gameport);
+}
+
+static int cobra_connect(struct gameport *gameport, struct gameport_driver *drv)
+{
+	struct cobra *cobra;
+	struct input_dev *input_dev;
+	unsigned int data[2];
+	int i, j;
+	int err;
+
+	cobra = kzalloc_obj(*cobra);
+	if (!cobra)
+		return -ENOMEM;
+
+	cobra->gameport = gameport;
+
+	gameport_set_drvdata(gameport, cobra);
+
+	err = gameport_open(gameport, drv, GAMEPORT_MODE_RAW);
+	if (err)
+		goto fail1;
+
+	cobra->exists = cobra_read_packet(gameport, data);
+
+	for (i = 0; i < 2; i++)
+		if ((cobra->exists >> i) & data[i] & 1) {
+			printk(KERN_WARNING "cobra.c: Device %d on %s has the Ext bit set. ID is: %d"
+				" Contact vojtech@ucw.cz\n", i, gameport->phys, (data[i] >> 2) & 7);
+			cobra->exists &= ~(1 << i);
+		}
+
+	if (!cobra->exists) {
+		err = -ENODEV;
+		goto fail2;
+	}
+
+	gameport_set_poll_handler(gameport, cobra_poll);
+	gameport_set_poll_interval(gameport, 20);
+
+	for (i = 0; i < 2; i++) {
+		if (~(cobra->exists >> i) & 1)
+			continue;
+
+		cobra->dev[i] = input_dev = input_allocate_device();
+		if (!input_dev) {
+			err = -ENOMEM;
+			goto fail3;
+		}
+
+		snprintf(cobra->phys[i], sizeof(cobra->phys[i]),
+			 "%s/input%d", gameport->phys, i);
+
+		input_dev->name = "Creative Labs Blaster GamePad Cobra";
+		input_dev->phys = cobra->phys[i];
+		input_dev->id.bustype = BUS_GAMEPORT;
+		input_dev->id.vendor = GAMEPORT_ID_VENDOR_CREATIVE;
+		input_dev->id.product = 0x0008;
+		input_dev->id.version = 0x0100;
+		input_dev->dev.parent = &gameport->dev;
+
+		input_set_drvdata(input_dev, cobra);
+
+		input_dev->open = cobra_open;
+		input_dev->close = cobra_close;
+
+		input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+		input_set_abs_params(input_dev, ABS_X, -1, 1, 0, 0);
+		input_set_abs_params(input_dev, ABS_Y, -1, 1, 0, 0);
+		for (j = 0; cobra_btn[j]; j++)
+			set_bit(cobra_btn[j], input_dev->keybit);
+
+		err = input_register_device(cobra->dev[i]);
+		if (err)
+			goto fail4;
+	}
+
+	return 0;
+
+ fail4:	input_free_device(cobra->dev[i]);
+ fail3:	while (--i >= 0)
+		if (cobra->dev[i])
+			input_unregister_device(cobra->dev[i]);
+ fail2:	gameport_close(gameport);
+ fail1:	gameport_set_drvdata(gameport, NULL);
+	kfree(cobra);
+	return err;
+}
+
+static void cobra_disconnect(struct gameport *gameport)
+{
+	struct cobra *cobra = gameport_get_drvdata(gameport);
+	int i;
+
+	for (i = 0; i < 2; i++)
+		if ((cobra->exists >> i) & 1)
+			input_unregister_device(cobra->dev[i]);
+	gameport_close(gameport);
+	gameport_set_drvdata(gameport, NULL);
+	kfree(cobra);
+}
+
+static struct gameport_driver cobra_drv = {
+	.driver		= {
+		.name	= "cobra",
+	},
+	.description	= DRIVER_DESC,
+	.connect	= cobra_connect,
+	.disconnect	= cobra_disconnect,
+};
+
+module_gameport_driver(cobra_drv);