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, 156 insertions, 0 deletions

diff --git a/drivers/input/keyboard/dlink-dir685-touchkeys.c b/drivers/input/keyboard/dlink-dir685-touchkeys.c
new file mode 100644
index 000000000..bf94367f6
--- /dev/null
+++ b/drivers/input/keyboard/dlink-dir685-touchkeys.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * D-Link DIR-685 router I2C-based Touchkeys input driver
+ * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * This is a one-off touchkey controller based on the Cypress Semiconductor
+ * CY8C214 MCU with some firmware in its internal 8KB flash. The circuit
+ * board inside the router is named E119921
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/string_choices.h>
+#include <linux/bitops.h>
+
+struct dir685_touchkeys {
+	struct device		*dev;
+	struct i2c_client	*client;
+	struct input_dev	*input;
+	unsigned long		cur_key;
+	u16			codes[7];
+};
+
+static irqreturn_t dir685_tk_irq_thread(int irq, void *data)
+{
+	struct dir685_touchkeys *tk = data;
+	const int num_bits = min_t(int, ARRAY_SIZE(tk->codes), 16);
+	unsigned long changed;
+	u8 buf[6];
+	unsigned long key;
+	int i;
+	int err;
+
+	memset(buf, 0, sizeof(buf));
+	err = i2c_master_recv(tk->client, buf, sizeof(buf));
+	if (err != sizeof(buf)) {
+		dev_err(tk->dev, "short read %d\n", err);
+		return IRQ_HANDLED;
+	}
+
+	dev_dbg(tk->dev, "IN: %*ph\n", (int)sizeof(buf), buf);
+	key = be16_to_cpup((__be16 *) &buf[4]);
+
+	/* Figure out if any bits went high or low since last message */
+	changed = tk->cur_key ^ key;
+	for_each_set_bit(i, &changed, num_bits) {
+		dev_dbg(tk->dev, "key %d is %s\n", i,
+			str_down_up(test_bit(i, &key)));
+		input_report_key(tk->input, tk->codes[i], test_bit(i, &key));
+	}
+
+	/* Store currently down keys */
+	tk->cur_key = key;
+	input_sync(tk->input);
+
+	return IRQ_HANDLED;
+}
+
+static int dir685_tk_probe(struct i2c_client *client)
+{
+	static const u8 bl_data[] = { 0xa7, 0x40 };
+	struct device *dev = &client->dev;
+	struct dir685_touchkeys *tk;
+	int err;
+	int i;
+
+	tk = devm_kzalloc(&client->dev, sizeof(*tk), GFP_KERNEL);
+	if (!tk)
+		return -ENOMEM;
+
+	tk->input = devm_input_allocate_device(dev);
+	if (!tk->input)
+		return -ENOMEM;
+
+	tk->client = client;
+	tk->dev = dev;
+
+	tk->input->keycodesize = sizeof(u16);
+	tk->input->keycodemax = ARRAY_SIZE(tk->codes);
+	tk->input->keycode = tk->codes;
+	tk->codes[0] = KEY_UP;
+	tk->codes[1] = KEY_DOWN;
+	tk->codes[2] = KEY_LEFT;
+	tk->codes[3] = KEY_RIGHT;
+	tk->codes[4] = KEY_ENTER;
+	tk->codes[5] = KEY_WPS_BUTTON;
+	/*
+	 * This key appears in the vendor driver, but I have
+	 * not been able to activate it.
+	 */
+	tk->codes[6] = KEY_RESERVED;
+
+	__set_bit(EV_KEY, tk->input->evbit);
+	for (i = 0; i < ARRAY_SIZE(tk->codes); i++)
+		__set_bit(tk->codes[i], tk->input->keybit);
+	__clear_bit(KEY_RESERVED, tk->input->keybit);
+
+	tk->input->name = "D-Link DIR-685 touchkeys";
+	tk->input->id.bustype = BUS_I2C;
+
+	err = input_register_device(tk->input);
+	if (err)
+		return err;
+
+	/* Set the brightness to max level */
+	err = i2c_master_send(client, bl_data, sizeof(bl_data));
+	if (err != sizeof(bl_data))
+		dev_warn(tk->dev, "error setting brightness level\n");
+
+	if (!client->irq) {
+		dev_err(dev, "no IRQ on the I2C device\n");
+		return -ENODEV;
+	}
+	err = devm_request_threaded_irq(dev, client->irq,
+					NULL, dir685_tk_irq_thread,
+					IRQF_ONESHOT,
+					"dir685-tk", tk);
+	if (err) {
+		dev_err(dev, "can't request IRQ\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id dir685_tk_id[] = {
+	{ .name = "dir685tk" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, dir685_tk_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id dir685_tk_of_match[] = {
+	{ .compatible = "dlink,dir685-touchkeys" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, dir685_tk_of_match);
+#endif
+
+static struct i2c_driver dir685_tk_i2c_driver = {
+	.driver = {
+		.name	= "dlink-dir685-touchkeys",
+		.of_match_table = of_match_ptr(dir685_tk_of_match),
+	},
+	.probe		= dir685_tk_probe,
+	.id_table	= dir685_tk_id,
+};
+module_i2c_driver(dir685_tk_i2c_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("D-Link DIR-685 touchkeys driver");
+MODULE_LICENSE("GPL");