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, 222 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ts4800-ts.c b/drivers/input/touchscreen/ts4800-ts.c
new file mode 100644
index 000000000..98422d1e8
--- /dev/null
+++ b/drivers/input/touchscreen/ts4800-ts.c
@@ -0,0 +1,222 @@
+/*
+ * Touchscreen driver for the TS-4800 board
+ *
+ * Copyright (c) 2015 - Savoir-faire Linux
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/bitops.h>
+#include <linux/input.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+/* polling interval in ms */
+#define POLL_INTERVAL		3
+
+#define DEBOUNCE_COUNT		1
+
+/* sensor values are 12-bit wide */
+#define MAX_12BIT		((1 << 12) - 1)
+
+#define PENDOWN_MASK		0x1
+
+#define X_OFFSET		0x0
+#define Y_OFFSET		0x2
+
+struct ts4800_ts {
+	struct input_dev        *input;
+	struct device           *dev;
+	char                    phys[32];
+
+	void __iomem            *base;
+	struct regmap           *regmap;
+	unsigned int            reg;
+	unsigned int            bit;
+
+	bool                    pendown;
+	int                     debounce;
+};
+
+static int ts4800_ts_open(struct input_dev *input_dev)
+{
+	struct ts4800_ts *ts = input_get_drvdata(input_dev);
+	int error;
+
+	ts->pendown = false;
+	ts->debounce = DEBOUNCE_COUNT;
+
+	error = regmap_update_bits(ts->regmap, ts->reg, ts->bit, ts->bit);
+	if (error) {
+		dev_warn(ts->dev, "Failed to enable touchscreen: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static void ts4800_ts_close(struct input_dev *input_dev)
+{
+	struct ts4800_ts *ts = input_get_drvdata(input_dev);
+	int ret;
+
+	ret = regmap_update_bits(ts->regmap, ts->reg, ts->bit, 0);
+	if (ret)
+		dev_warn(ts->dev, "Failed to disable touchscreen\n");
+
+}
+
+static void ts4800_ts_poll(struct input_dev *input_dev)
+{
+	struct ts4800_ts *ts = input_get_drvdata(input_dev);
+	u16 last_x = readw(ts->base + X_OFFSET);
+	u16 last_y = readw(ts->base + Y_OFFSET);
+	bool pendown = last_x & PENDOWN_MASK;
+
+	if (pendown) {
+		if (ts->debounce) {
+			ts->debounce--;
+			return;
+		}
+
+		if (!ts->pendown) {
+			input_report_key(input_dev, BTN_TOUCH, 1);
+			ts->pendown = true;
+		}
+
+		last_x = ((~last_x) >> 4) & MAX_12BIT;
+		last_y = ((~last_y) >> 4) & MAX_12BIT;
+
+		input_report_abs(input_dev, ABS_X, last_x);
+		input_report_abs(input_dev, ABS_Y, last_y);
+		input_sync(input_dev);
+	} else if (ts->pendown) {
+		ts->pendown = false;
+		ts->debounce = DEBOUNCE_COUNT;
+		input_report_key(input_dev, BTN_TOUCH, 0);
+		input_sync(input_dev);
+	}
+}
+
+static int ts4800_parse_dt(struct platform_device *pdev,
+			   struct ts4800_ts *ts)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	u32 reg, bit;
+	int error;
+
+	struct device_node *syscon_np __free(device_node) =
+		of_parse_phandle(np, "syscon", 0);
+	if (!syscon_np) {
+		dev_err(dev, "no syscon property\n");
+		return -ENODEV;
+	}
+
+	ts->regmap = syscon_node_to_regmap(syscon_np);
+	if (IS_ERR(ts->regmap)) {
+		dev_err(dev, "cannot get parent's regmap\n");
+		return PTR_ERR(ts->regmap);
+	}
+
+	error = of_property_read_u32_index(np, "syscon", 1, &reg);
+	if (error < 0) {
+		dev_err(dev, "no offset in syscon\n");
+		return error;
+	}
+
+	ts->reg = reg;
+
+	error = of_property_read_u32_index(np, "syscon", 2, &bit);
+	if (error < 0) {
+		dev_err(dev, "no bit in syscon\n");
+		return error;
+	}
+
+	ts->bit = BIT(bit);
+
+	return 0;
+}
+
+static int ts4800_ts_probe(struct platform_device *pdev)
+{
+	struct input_dev *input_dev;
+	struct ts4800_ts *ts;
+	int error;
+
+	ts = devm_kzalloc(&pdev->dev, sizeof(*ts), GFP_KERNEL);
+	if (!ts)
+		return -ENOMEM;
+
+	error = ts4800_parse_dt(pdev, ts);
+	if (error)
+		return error;
+
+	ts->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ts->base))
+		return PTR_ERR(ts->base);
+
+	input_dev = devm_input_allocate_device(&pdev->dev);
+	if (!input_dev)
+		return -ENOMEM;
+
+	snprintf(ts->phys, sizeof(ts->phys), "%s/input0", dev_name(&pdev->dev));
+	ts->input = input_dev;
+	ts->dev = &pdev->dev;
+
+	input_set_drvdata(input_dev, ts);
+
+	input_dev->name = "TS-4800 Touchscreen";
+	input_dev->phys = ts->phys;
+
+	input_dev->open = ts4800_ts_open;
+	input_dev->close = ts4800_ts_close;
+
+	input_set_capability(input_dev, EV_KEY, BTN_TOUCH);
+	input_set_abs_params(input_dev, ABS_X, 0, MAX_12BIT, 0, 0);
+	input_set_abs_params(input_dev, ABS_Y, 0, MAX_12BIT, 0, 0);
+
+	error = input_setup_polling(input_dev, ts4800_ts_poll);
+	if (error) {
+		dev_err(&pdev->dev, "Unable to set up polling: %d\n", error);
+		return error;
+	}
+
+	input_set_poll_interval(input_dev, POLL_INTERVAL);
+
+	error = input_register_device(input_dev);
+	if (error) {
+		dev_err(&pdev->dev,
+			"Unable to register input device: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id ts4800_ts_of_match[] = {
+	{ .compatible = "technologic,ts4800-ts", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ts4800_ts_of_match);
+
+static struct platform_driver ts4800_ts_driver = {
+	.driver = {
+		.name = "ts4800-ts",
+		.of_match_table = ts4800_ts_of_match,
+	},
+	.probe = ts4800_ts_probe,
+};
+module_platform_driver(ts4800_ts_driver);
+
+MODULE_AUTHOR("Damien Riegel <damien.riegel@savoirfairelinux.com>");
+MODULE_DESCRIPTION("TS-4800 Touchscreen Driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:ts4800_ts");