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, 142 insertions, 0 deletions

diff --git a/drivers/hid/hid-vivaldi-common.c b/drivers/hid/hid-vivaldi-common.c
new file mode 100644
index 000000000..b12bb5cc0
--- /dev/null
+++ b/drivers/hid/hid-vivaldi-common.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for ChromeOS HID Vivaldi keyboards
+ *
+ * Copyright (C) 2022 Google, Inc
+ */
+
+#include <linux/export.h>
+#include <linux/hid.h>
+#include <linux/input/vivaldi-fmap.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include "hid-vivaldi-common.h"
+
+#define MIN_FN_ROW_KEY 1
+#define MAX_FN_ROW_KEY VIVALDI_MAX_FUNCTION_ROW_KEYS
+#define HID_VD_FN_ROW_PHYSMAP 0x00000001
+#define HID_USAGE_FN_ROW_PHYSMAP (HID_UP_GOOGLEVENDOR | HID_VD_FN_ROW_PHYSMAP)
+
+/**
+ * vivaldi_feature_mapping - Fill out vivaldi keymap data exposed via HID
+ * @hdev: HID device to parse
+ * @field: HID field to parse
+ * @usage: HID usage to parse
+ *
+ * Note: this function assumes that driver data attached to @hdev contains an
+ * instance of &struct vivaldi_data at the very beginning.
+ */
+void vivaldi_feature_mapping(struct hid_device *hdev,
+			     struct hid_field *field, struct hid_usage *usage)
+{
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+	struct hid_report *report = field->report;
+	u8 *report_data, *buf;
+	u32 report_len;
+	unsigned int fn_key;
+	int ret;
+
+	if (field->logical != HID_USAGE_FN_ROW_PHYSMAP ||
+	    (usage->hid & HID_USAGE_PAGE) != HID_UP_ORDINAL)
+		return;
+
+	fn_key = usage->hid & HID_USAGE;
+	if (fn_key < MIN_FN_ROW_KEY || fn_key > MAX_FN_ROW_KEY)
+		return;
+
+	if (fn_key > data->num_function_row_keys)
+		data->num_function_row_keys = fn_key;
+
+	report_data = buf = hid_alloc_report_buf(report, GFP_KERNEL);
+	if (!report_data)
+		return;
+
+	report_len = hid_report_len(report);
+	if (!report->id) {
+		/*
+		 * hid_hw_raw_request() will stuff report ID (which will be 0)
+		 * into the first byte of the buffer even for unnumbered
+		 * reports, so we need to account for this to avoid getting
+		 * -EOVERFLOW in return.
+		 * Note that hid_alloc_report_buf() adds 7 bytes to the size
+		 * so we can safely say that we have space for an extra byte.
+		 */
+		report_len++;
+	}
+
+	ret = hid_hw_raw_request(hdev, report->id, report_data,
+				 report_len, HID_FEATURE_REPORT,
+				 HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		dev_warn(&hdev->dev, "failed to fetch feature %d\n",
+			 field->report->id);
+		goto out;
+	}
+
+	if (!report->id) {
+		/*
+		 * Undo the damage from hid_hw_raw_request() for unnumbered
+		 * reports.
+		 */
+		report_data++;
+		report_len--;
+	}
+
+	ret = hid_report_raw_event(hdev, HID_FEATURE_REPORT, report_data,
+				   report_len, report_len, 0);
+	if (ret) {
+		dev_warn(&hdev->dev, "failed to report feature %d\n",
+			 field->report->id);
+		goto out;
+	}
+
+	data->function_row_physmap[fn_key - MIN_FN_ROW_KEY] =
+		field->value[usage->usage_index];
+
+out:
+	kfree(buf);
+}
+EXPORT_SYMBOL_GPL(vivaldi_feature_mapping);
+
+static ssize_t function_row_physmap_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct hid_device *hdev = to_hid_device(dev);
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+
+	return vivaldi_function_row_physmap_show(data, buf);
+}
+
+static DEVICE_ATTR_RO(function_row_physmap);
+static struct attribute *vivaldi_sysfs_attrs[] = {
+	&dev_attr_function_row_physmap.attr,
+	NULL
+};
+
+static umode_t vivaldi_is_visible(struct kobject *kobj, struct attribute *attr,
+				  int n)
+{
+	struct hid_device *hdev = to_hid_device(kobj_to_dev(kobj));
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+
+	if (!data->num_function_row_keys)
+		return 0;
+	return attr->mode;
+}
+
+static const struct attribute_group vivaldi_attribute_group = {
+	.attrs = vivaldi_sysfs_attrs,
+	.is_visible = vivaldi_is_visible,
+};
+
+const struct attribute_group *vivaldi_attribute_groups[] = {
+	&vivaldi_attribute_group,
+	NULL,
+};
+EXPORT_SYMBOL_GPL(vivaldi_attribute_groups);
+
+MODULE_DESCRIPTION("Helpers for ChromeOS HID Vivaldi keyboards");
+MODULE_LICENSE("GPL");