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, 208 insertions, 0 deletions

diff --git a/drivers/input/touchscreen.c b/drivers/input/touchscreen.c
new file mode 100644
index 000000000..d699b24bb
--- /dev/null
+++ b/drivers/input/touchscreen.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Generic helper functions for touchscreens and other two-dimensional
+ *  pointing devices
+ *
+ *  Copyright (c) 2014 Sebastian Reichel <sre@kernel.org>
+ */
+
+#include <linux/export.h>
+#include <linux/property.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/input/touchscreen.h>
+#include <linux/module.h>
+
+static bool touchscreen_get_prop_u32(struct device *dev,
+				     const char *property,
+				     unsigned int default_value,
+				     unsigned int *value)
+{
+	u32 val;
+	int error;
+
+	error = device_property_read_u32(dev, property, &val);
+	if (error) {
+		*value = default_value;
+		return false;
+	}
+
+	*value = val;
+	return true;
+}
+
+static void touchscreen_set_params(struct input_dev *dev,
+				   unsigned long axis,
+				   int min, int max, int fuzz)
+{
+	struct input_absinfo *absinfo;
+
+	if (!test_bit(axis, dev->absbit)) {
+		dev_warn(&dev->dev,
+			 "Parameters are specified but the axis %lu is not set up\n",
+			 axis);
+		return;
+	}
+
+	absinfo = &dev->absinfo[axis];
+	absinfo->minimum = min;
+	absinfo->maximum = max;
+	absinfo->fuzz = fuzz;
+}
+
+/**
+ * touchscreen_parse_properties - parse common touchscreen properties
+ * @input: input device that should be parsed
+ * @multitouch: specifies whether parsed properties should be applied to
+ *	single-touch or multi-touch axes
+ * @prop: pointer to a struct touchscreen_properties into which to store
+ *	axis swap and invert info for use with touchscreen_report_x_y();
+ *	or %NULL
+ *
+ * This function parses common properties for touchscreens and sets up the
+ * input device accordingly. The function keeps previously set up default
+ * values if no value is specified.
+ */
+void touchscreen_parse_properties(struct input_dev *input, bool multitouch,
+				  struct touchscreen_properties *prop)
+{
+	struct device *dev = input->dev.parent;
+	struct input_absinfo *absinfo;
+	unsigned int axis, axis_x, axis_y;
+	unsigned int minimum, maximum, fuzz;
+	bool data_present;
+
+	input_alloc_absinfo(input);
+	if (!input->absinfo)
+		return;
+
+	axis_x = multitouch ? ABS_MT_POSITION_X : ABS_X;
+	axis_y = multitouch ? ABS_MT_POSITION_Y : ABS_Y;
+
+	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-x",
+						input_abs_get_min(input, axis_x),
+						&minimum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-x",
+						 input_abs_get_max(input,
+								   axis_x) + 1,
+						 &maximum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-x",
+						 input_abs_get_fuzz(input, axis_x),
+						 &fuzz);
+	if (data_present)
+		touchscreen_set_params(input, axis_x, minimum, maximum - 1, fuzz);
+
+	data_present = touchscreen_get_prop_u32(dev, "touchscreen-min-y",
+						input_abs_get_min(input, axis_y),
+						&minimum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-size-y",
+						 input_abs_get_max(input,
+								   axis_y) + 1,
+						 &maximum);
+	data_present |= touchscreen_get_prop_u32(dev, "touchscreen-fuzz-y",
+						 input_abs_get_fuzz(input, axis_y),
+						 &fuzz);
+	if (data_present)
+		touchscreen_set_params(input, axis_y, minimum, maximum - 1, fuzz);
+
+	axis = multitouch ? ABS_MT_PRESSURE : ABS_PRESSURE;
+	data_present = touchscreen_get_prop_u32(dev,
+						"touchscreen-max-pressure",
+						input_abs_get_max(input, axis),
+						&maximum);
+	data_present |= touchscreen_get_prop_u32(dev,
+						 "touchscreen-fuzz-pressure",
+						 input_abs_get_fuzz(input, axis),
+						 &fuzz);
+	if (data_present)
+		touchscreen_set_params(input, axis, 0, maximum, fuzz);
+
+	if (!prop)
+		return;
+
+	prop->max_x = input_abs_get_max(input, axis_x);
+	prop->max_y = input_abs_get_max(input, axis_y);
+
+	prop->invert_x =
+		device_property_read_bool(dev, "touchscreen-inverted-x");
+	if (prop->invert_x) {
+		absinfo = &input->absinfo[axis_x];
+		absinfo->maximum -= absinfo->minimum;
+		absinfo->minimum = 0;
+	}
+
+	prop->invert_y =
+		device_property_read_bool(dev, "touchscreen-inverted-y");
+	if (prop->invert_y) {
+		absinfo = &input->absinfo[axis_y];
+		absinfo->maximum -= absinfo->minimum;
+		absinfo->minimum = 0;
+	}
+
+	prop->swap_x_y =
+		device_property_read_bool(dev, "touchscreen-swapped-x-y");
+	if (prop->swap_x_y)
+		swap(input->absinfo[axis_x], input->absinfo[axis_y]);
+}
+EXPORT_SYMBOL(touchscreen_parse_properties);
+
+static void
+touchscreen_apply_prop_to_x_y(const struct touchscreen_properties *prop,
+			      unsigned int *x, unsigned int *y)
+{
+	if (prop->invert_x)
+		*x = prop->max_x - *x;
+
+	if (prop->invert_y)
+		*y = prop->max_y - *y;
+
+	if (prop->swap_x_y)
+		swap(*x, *y);
+}
+
+/**
+ * touchscreen_set_mt_pos - Set input_mt_pos coordinates
+ * @pos: input_mt_pos to set coordinates of
+ * @prop: pointer to a struct touchscreen_properties
+ * @x: X coordinate to store in pos
+ * @y: Y coordinate to store in pos
+ *
+ * Adjust the passed in x and y values applying any axis inversion and
+ * swapping requested in the passed in touchscreen_properties and store
+ * the result in a struct input_mt_pos.
+ */
+void touchscreen_set_mt_pos(struct input_mt_pos *pos,
+			    const struct touchscreen_properties *prop,
+			    unsigned int x, unsigned int y)
+{
+	touchscreen_apply_prop_to_x_y(prop, &x, &y);
+	pos->x = x;
+	pos->y = y;
+}
+EXPORT_SYMBOL(touchscreen_set_mt_pos);
+
+/**
+ * touchscreen_report_pos - Report touchscreen coordinates
+ * @input: input_device to report coordinates for
+ * @prop: pointer to a struct touchscreen_properties
+ * @x: X coordinate to report
+ * @y: Y coordinate to report
+ * @multitouch: Report coordinates on single-touch or multi-touch axes
+ *
+ * Adjust the passed in x and y values applying any axis inversion and
+ * swapping requested in the passed in touchscreen_properties and then
+ * report the resulting coordinates on the input_dev's x and y axis.
+ */
+void touchscreen_report_pos(struct input_dev *input,
+			    const struct touchscreen_properties *prop,
+			    unsigned int x, unsigned int y,
+			    bool multitouch)
+{
+	touchscreen_apply_prop_to_x_y(prop, &x, &y);
+	input_report_abs(input, multitouch ? ABS_MT_POSITION_X : ABS_X, x);
+	input_report_abs(input, multitouch ? ABS_MT_POSITION_Y : ABS_Y, y);
+}
+EXPORT_SYMBOL(touchscreen_report_pos);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Helper functions for touchscreens and other devices");