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, 272 insertions, 0 deletions

diff --git a/drivers/usb/misc/emi62.c b/drivers/usb/misc/emi62.c
new file mode 100644
index 000000000..3eea60437
--- /dev/null
+++ b/drivers/usb/misc/emi62.c
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0
+/* 
+ * Emagic EMI 2|6 usb audio interface firmware loader.
+ * Copyright (C) 2002
+ * 	Tapio Laxström (tapio.laxstrom@iptime.fi)
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/delay.h>
+#include <linux/firmware.h>
+#include <linux/ihex.h>
+
+/* include firmware (variables)*/
+
+/* FIXME: This is quick and dirty solution! */
+#define SPDIF	/* if you want SPDIF comment next line */
+//#undef SPDIF	/* if you want MIDI uncomment this line */ 
+
+#ifdef SPDIF
+#define FIRMWARE_FW "emi62/spdif.fw"
+#else
+#define FIRMWARE_FW "emi62/midi.fw"
+#endif
+
+#define EMI62_VENDOR_ID 		0x086a  /* Emagic Soft-und Hardware GmBH */
+#define EMI62_PRODUCT_ID		0x0110	/* EMI 6|2m without firmware */
+
+#define ANCHOR_LOAD_INTERNAL	0xA0	/* Vendor specific request code for Anchor Upload/Download (This one is implemented in the core) */
+#define ANCHOR_LOAD_EXTERNAL	0xA3	/* This command is not implemented in the core. Requires firmware */
+#define ANCHOR_LOAD_FPGA	0xA5	/* This command is not implemented in the core. Requires firmware. Emagic extension */
+#define MAX_INTERNAL_ADDRESS	0x1B3F	/* This is the highest internal RAM address for the AN2131Q */
+#define CPUCS_REG		0x7F92  /* EZ-USB Control and Status Register.  Bit 0 controls 8051 reset */ 
+#define INTERNAL_RAM(address)   (address <= MAX_INTERNAL_ADDRESS)
+
+static int emi62_writememory(struct usb_device *dev, int address,
+			     const unsigned char *data, int length,
+			     __u8 bRequest);
+static int emi62_set_reset(struct usb_device *dev, unsigned char reset_bit);
+static int emi62_load_firmware (struct usb_device *dev);
+static int emi62_probe(struct usb_interface *intf, const struct usb_device_id *id);
+static void emi62_disconnect(struct usb_interface *intf);
+
+/* thanks to drivers/usb/serial/keyspan_pda.c code */
+static int emi62_writememory(struct usb_device *dev, int address,
+			     const unsigned char *data, int length,
+			     __u8 request)
+{
+	int result;
+	unsigned char *buffer =  kmemdup(data, length, GFP_KERNEL);
+
+	if (!buffer) {
+		dev_err(&dev->dev, "kmalloc(%d) failed.\n", length);
+		return -ENOMEM;
+	}
+	/* Note: usb_control_msg returns negative value on error or length of the
+	 * 		 data that was written! */
+	result = usb_control_msg (dev, usb_sndctrlpipe(dev, 0), request, 0x40, address, 0, buffer, length, 300);
+	kfree (buffer);
+	return result;
+}
+
+/* thanks to drivers/usb/serial/keyspan_pda.c code */
+static int emi62_set_reset (struct usb_device *dev, unsigned char reset_bit)
+{
+	int response;
+	dev_info(&dev->dev, "%s - %d\n", __func__, reset_bit);
+	
+	response = emi62_writememory (dev, CPUCS_REG, &reset_bit, 1, 0xa0);
+	if (response < 0)
+		dev_err(&dev->dev, "set_reset (%d) failed\n", reset_bit);
+	return response;
+}
+
+#define FW_LOAD_SIZE		1023
+
+static int emi62_load_firmware (struct usb_device *dev)
+{
+	const struct firmware *loader_fw = NULL;
+	const struct firmware *bitstream_fw = NULL;
+	const struct firmware *firmware_fw = NULL;
+	const struct ihex_binrec *rec;
+	int err = -ENOMEM;
+	int i;
+	__u32 addr;	/* Address to write */
+	__u8 *buf;
+
+	dev_dbg(&dev->dev, "load_firmware\n");
+	buf = kmalloc(FW_LOAD_SIZE, GFP_KERNEL);
+	if (!buf)
+		goto wraperr;
+
+	err = request_ihex_firmware(&loader_fw, "emi62/loader.fw", &dev->dev);
+	if (err)
+		goto nofw;
+
+	err = request_ihex_firmware(&bitstream_fw, "emi62/bitstream.fw",
+				    &dev->dev);
+	if (err)
+		goto nofw;
+
+	err = request_ihex_firmware(&firmware_fw, FIRMWARE_FW, &dev->dev);
+	if (err) {
+	nofw:
+		goto wraperr;
+	}
+
+	/* Assert reset (stop the CPU in the EMI) */
+	err = emi62_set_reset(dev,1);
+	if (err < 0)
+		goto wraperr;
+
+	rec = (const struct ihex_binrec *)loader_fw->data;
+
+	/* 1. We need to put the loader for the FPGA into the EZ-USB */
+	while (rec) {
+		err = emi62_writememory(dev, be32_to_cpu(rec->addr),
+					rec->data, be16_to_cpu(rec->len),
+					ANCHOR_LOAD_INTERNAL);
+		if (err < 0)
+			goto wraperr;
+		rec = ihex_next_binrec(rec);
+	}
+
+	/* De-assert reset (let the CPU run) */
+	err = emi62_set_reset(dev,0);
+	if (err < 0)
+		goto wraperr;
+	msleep(250);	/* let device settle */
+
+	/* 2. We upload the FPGA firmware into the EMI
+	 * Note: collect up to 1023 (yes!) bytes and send them with
+	 * a single request. This is _much_ faster! */
+	rec = (const struct ihex_binrec *)bitstream_fw->data;
+	do {
+		i = 0;
+		addr = be32_to_cpu(rec->addr);
+
+		/* intel hex records are terminated with type 0 element */
+		while (rec && (i + be16_to_cpu(rec->len) < FW_LOAD_SIZE)) {
+			memcpy(buf + i, rec->data, be16_to_cpu(rec->len));
+			i += be16_to_cpu(rec->len);
+			rec = ihex_next_binrec(rec);
+		}
+		err = emi62_writememory(dev, addr, buf, i, ANCHOR_LOAD_FPGA);
+		if (err < 0)
+			goto wraperr;
+	} while (rec);
+
+	/* Assert reset (stop the CPU in the EMI) */
+	err = emi62_set_reset(dev,1);
+	if (err < 0)
+		goto wraperr;
+
+	/* 3. We need to put the loader for the firmware into the EZ-USB (again...) */
+	for (rec = (const struct ihex_binrec *)loader_fw->data;
+	     rec; rec = ihex_next_binrec(rec)) {
+		err = emi62_writememory(dev, be32_to_cpu(rec->addr),
+					rec->data, be16_to_cpu(rec->len),
+					ANCHOR_LOAD_INTERNAL);
+		if (err < 0)
+			goto wraperr;
+	}
+
+	/* De-assert reset (let the CPU run) */
+	err = emi62_set_reset(dev,0);
+	if (err < 0)
+		goto wraperr;
+	msleep(250);	/* let device settle */
+
+	/* 4. We put the part of the firmware that lies in the external RAM into the EZ-USB */
+
+	for (rec = (const struct ihex_binrec *)firmware_fw->data;
+	     rec; rec = ihex_next_binrec(rec)) {
+		if (!INTERNAL_RAM(be32_to_cpu(rec->addr))) {
+			err = emi62_writememory(dev, be32_to_cpu(rec->addr),
+						rec->data, be16_to_cpu(rec->len),
+						ANCHOR_LOAD_EXTERNAL);
+			if (err < 0)
+				goto wraperr;
+		}
+	}
+
+	/* Assert reset (stop the CPU in the EMI) */
+	err = emi62_set_reset(dev,1);
+	if (err < 0)
+		goto wraperr;
+
+	for (rec = (const struct ihex_binrec *)firmware_fw->data;
+	     rec; rec = ihex_next_binrec(rec)) {
+		if (INTERNAL_RAM(be32_to_cpu(rec->addr))) {
+			err = emi62_writememory(dev, be32_to_cpu(rec->addr),
+						rec->data, be16_to_cpu(rec->len),
+						ANCHOR_LOAD_EXTERNAL);
+			if (err < 0)
+				goto wraperr;
+		}
+	}
+
+	/* De-assert reset (let the CPU run) */
+	err = emi62_set_reset(dev,0);
+	if (err < 0)
+		goto wraperr;
+	msleep(250);	/* let device settle */
+
+	release_firmware(loader_fw);
+	release_firmware(bitstream_fw);
+	release_firmware(firmware_fw);
+
+	kfree(buf);
+
+	/* return 1 to fail the driver inialization
+	 * and give real driver change to load */
+	return 1;
+
+wraperr:
+	if (err < 0)
+		dev_err(&dev->dev,"%s - error loading firmware: error = %d\n",
+			__func__, err);
+	release_firmware(loader_fw);
+	release_firmware(bitstream_fw);
+	release_firmware(firmware_fw);
+
+	kfree(buf);
+	dev_err(&dev->dev, "Error\n");
+	return err;
+}
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(EMI62_VENDOR_ID, EMI62_PRODUCT_ID) },
+	{ }                                             /* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE (usb, id_table);
+
+static int emi62_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	struct usb_device *dev = interface_to_usbdev(intf);
+	dev_dbg(&intf->dev, "emi62_probe\n");
+
+	dev_info(&intf->dev, "%s start\n", __func__);
+
+	emi62_load_firmware(dev);
+
+	/* do not return the driver context, let real audio driver do that */
+	return -EIO;
+}
+
+static void emi62_disconnect(struct usb_interface *intf)
+{
+}
+
+static struct usb_driver emi62_driver = {
+	.name		= "emi62 - firmware loader",
+	.probe		= emi62_probe,
+	.disconnect	= emi62_disconnect,
+	.id_table	= id_table,
+};
+
+module_usb_driver(emi62_driver);
+
+MODULE_AUTHOR("Tapio Laxström");
+MODULE_DESCRIPTION("Emagic EMI 6|2m firmware loader.");
+MODULE_LICENSE("GPL");
+
+MODULE_FIRMWARE("emi62/loader.fw");
+MODULE_FIRMWARE("emi62/bitstream.fw");
+MODULE_FIRMWARE(FIRMWARE_FW);
+/* vi:ai:syntax=c:sw=8:ts=8:tw=80
+ */