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, 212 insertions, 0 deletions

diff --git a/drivers/hid/hid-wiimote-debug.c b/drivers/hid/hid-wiimote-debug.c
new file mode 100644
index 000000000..5f7491778
--- /dev/null
+++ b/drivers/hid/hid-wiimote-debug.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Debug support for HID Nintendo Wii / Wii U peripherals
+ * Copyright (c) 2011-2013 David Herrmann <dh.herrmann@gmail.com>
+ */
+
+/*
+ */
+
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include "hid-wiimote.h"
+
+struct wiimote_debug {
+	struct wiimote_data *wdata;
+	struct dentry *eeprom;
+	struct dentry *drm;
+};
+
+static ssize_t wiidebug_eeprom_read(struct file *f, char __user *u, size_t s,
+								loff_t *off)
+{
+	struct wiimote_debug *dbg = f->private_data;
+	struct wiimote_data *wdata = dbg->wdata;
+	unsigned long flags;
+	ssize_t ret;
+	char buf[16];
+	__u16 size = 0;
+
+	if (s == 0)
+		return -EINVAL;
+	if (*off > 0xffffff)
+		return 0;
+	if (s > 16)
+		s = 16;
+
+	ret = wiimote_cmd_acquire(wdata);
+	if (ret)
+		return ret;
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->state.cmd_read_size = s;
+	wdata->state.cmd_read_buf = buf;
+	wiimote_cmd_set(wdata, WIIPROTO_REQ_RMEM, *off & 0xffff);
+	wiiproto_req_reeprom(wdata, *off, s);
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	ret = wiimote_cmd_wait(wdata);
+	if (!ret)
+		size = wdata->state.cmd_read_size;
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->state.cmd_read_buf = NULL;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	wiimote_cmd_release(wdata);
+
+	if (ret)
+		return ret;
+	else if (size == 0)
+		return -EIO;
+
+	if (copy_to_user(u, buf, size))
+		return -EFAULT;
+
+	*off += size;
+	ret = size;
+
+	return ret;
+}
+
+static const struct file_operations wiidebug_eeprom_fops = {
+	.owner = THIS_MODULE,
+	.open = simple_open,
+	.read = wiidebug_eeprom_read,
+	.llseek = generic_file_llseek,
+};
+
+static const char *wiidebug_drmmap[] = {
+	[WIIPROTO_REQ_NULL] = "NULL",
+	[WIIPROTO_REQ_DRM_K] = "K",
+	[WIIPROTO_REQ_DRM_KA] = "KA",
+	[WIIPROTO_REQ_DRM_KE] = "KE",
+	[WIIPROTO_REQ_DRM_KAI] = "KAI",
+	[WIIPROTO_REQ_DRM_KEE] = "KEE",
+	[WIIPROTO_REQ_DRM_KAE] = "KAE",
+	[WIIPROTO_REQ_DRM_KIE] = "KIE",
+	[WIIPROTO_REQ_DRM_KAIE] = "KAIE",
+	[WIIPROTO_REQ_DRM_E] = "E",
+	[WIIPROTO_REQ_DRM_SKAI1] = "SKAI1",
+	[WIIPROTO_REQ_DRM_SKAI2] = "SKAI2",
+	[WIIPROTO_REQ_MAX] = NULL
+};
+
+static int wiidebug_drm_show(struct seq_file *f, void *p)
+{
+	struct wiimote_debug *dbg = f->private;
+	const char *str = NULL;
+	unsigned long flags;
+	__u8 drm;
+
+	spin_lock_irqsave(&dbg->wdata->state.lock, flags);
+	drm = dbg->wdata->state.drm;
+	spin_unlock_irqrestore(&dbg->wdata->state.lock, flags);
+
+	if (drm < WIIPROTO_REQ_MAX)
+		str = wiidebug_drmmap[drm];
+	if (!str)
+		str = "unknown";
+
+	seq_printf(f, "%s\n", str);
+
+	return 0;
+}
+
+static int wiidebug_drm_open(struct inode *i, struct file *f)
+{
+	return single_open(f, wiidebug_drm_show, i->i_private);
+}
+
+static ssize_t wiidebug_drm_write(struct file *f, const char __user *u,
+							size_t s, loff_t *off)
+{
+	struct seq_file *sf = f->private_data;
+	struct wiimote_debug *dbg = sf->private;
+	unsigned long flags;
+	char buf[16];
+	ssize_t len;
+	int i;
+
+	if (s == 0)
+		return -EINVAL;
+
+	len = min((size_t) 15, s);
+	if (copy_from_user(buf, u, len))
+		return -EFAULT;
+
+	buf[len] = 0;
+
+	for (i = 0; i < WIIPROTO_REQ_MAX; ++i) {
+		if (!wiidebug_drmmap[i])
+			continue;
+		if (!strcasecmp(buf, wiidebug_drmmap[i]))
+			break;
+	}
+
+	if (i == WIIPROTO_REQ_MAX)
+		i = simple_strtoul(buf, NULL, 16);
+
+	spin_lock_irqsave(&dbg->wdata->state.lock, flags);
+	dbg->wdata->state.flags &= ~WIIPROTO_FLAG_DRM_LOCKED;
+	wiiproto_req_drm(dbg->wdata, (__u8) i);
+	if (i != WIIPROTO_REQ_NULL)
+		dbg->wdata->state.flags |= WIIPROTO_FLAG_DRM_LOCKED;
+	spin_unlock_irqrestore(&dbg->wdata->state.lock, flags);
+
+	return len;
+}
+
+static const struct file_operations wiidebug_drm_fops = {
+	.owner = THIS_MODULE,
+	.open = wiidebug_drm_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.write = wiidebug_drm_write,
+	.release = single_release,
+};
+
+int wiidebug_init(struct wiimote_data *wdata)
+{
+	struct wiimote_debug *dbg;
+	unsigned long flags;
+
+	dbg = kzalloc_obj(*dbg);
+	if (!dbg)
+		return -ENOMEM;
+
+	dbg->wdata = wdata;
+
+	dbg->eeprom = debugfs_create_file("eeprom", S_IRUSR,
+		dbg->wdata->hdev->debug_dir, dbg, &wiidebug_eeprom_fops);
+
+	dbg->drm = debugfs_create_file("drm", S_IRUSR,
+			dbg->wdata->hdev->debug_dir, dbg, &wiidebug_drm_fops);
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->debug = dbg;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	return 0;
+
+}
+
+void wiidebug_deinit(struct wiimote_data *wdata)
+{
+	struct wiimote_debug *dbg = wdata->debug;
+	unsigned long flags;
+
+	if (!dbg)
+		return;
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->debug = NULL;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	debugfs_remove(dbg->drm);
+	debugfs_remove(dbg->eeprom);
+	kfree(dbg);
+}