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, 152 insertions, 0 deletions

diff --git a/drivers/usb/misc/ezusb.c b/drivers/usb/misc/ezusb.c
new file mode 100644
index 000000000..7ab4856ab
--- /dev/null
+++ b/drivers/usb/misc/ezusb.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * EZ-USB specific functions used by some of the USB to Serial drivers.
+ *
+ * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/firmware.h>
+#include <linux/ihex.h>
+#include <linux/usb/ezusb.h>
+
+struct ezusb_fx_type {
+	/* EZ-USB Control and Status Register.  Bit 0 controls 8051 reset */
+	unsigned short cpucs_reg;
+	unsigned short max_internal_adress;
+};
+
+static const struct ezusb_fx_type ezusb_fx1 = {
+	.cpucs_reg = 0x7F92,
+	.max_internal_adress = 0x1B3F,
+};
+
+/* Commands for writing to memory */
+#define WRITE_INT_RAM 0xA0
+#define WRITE_EXT_RAM 0xA3
+
+static int ezusb_writememory(struct usb_device *dev, int address,
+				unsigned char *data, int length, __u8 request)
+{
+	if (!dev)
+		return -ENODEV;
+
+	return usb_control_msg_send(dev, 0, request,
+				 USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
+				 address, 0, data, length, 3000, GFP_KERNEL);
+}
+
+static int ezusb_set_reset(struct usb_device *dev, unsigned short cpucs_reg,
+			   unsigned char reset_bit)
+{
+	int response = ezusb_writememory(dev, cpucs_reg, &reset_bit, 1, WRITE_INT_RAM);
+	if (response < 0)
+		dev_err(&dev->dev, "%s-%d failed: %d\n",
+						__func__, reset_bit, response);
+	return response;
+}
+
+int ezusb_fx1_set_reset(struct usb_device *dev, unsigned char reset_bit)
+{
+	return ezusb_set_reset(dev, ezusb_fx1.cpucs_reg, reset_bit);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx1_set_reset);
+
+static int ezusb_ihex_firmware_download(struct usb_device *dev,
+					struct ezusb_fx_type fx,
+					const char *firmware_path)
+{
+	int ret = -ENOENT;
+	const struct firmware *firmware = NULL;
+	const struct ihex_binrec *record;
+
+	if (request_ihex_firmware(&firmware, firmware_path,
+				  &dev->dev)) {
+		dev_err(&dev->dev,
+			"%s - request \"%s\" failed\n",
+			__func__, firmware_path);
+		goto out;
+	}
+
+	ret = ezusb_set_reset(dev, fx.cpucs_reg, 0);
+	if (ret < 0)
+		goto out;
+
+	record = (const struct ihex_binrec *)firmware->data;
+	for (; record; record = ihex_next_binrec(record)) {
+		if (be32_to_cpu(record->addr) > fx.max_internal_adress) {
+			ret = ezusb_writememory(dev, be32_to_cpu(record->addr),
+						(unsigned char *)record->data,
+						be16_to_cpu(record->len), WRITE_EXT_RAM);
+			if (ret < 0) {
+				dev_err(&dev->dev, "%s - ezusb_writememory "
+					"failed writing internal memory "
+					"(%d %04X %p %d)\n", __func__, ret,
+					be32_to_cpu(record->addr), record->data,
+					be16_to_cpu(record->len));
+				goto out;
+			}
+		}
+	}
+
+	ret = ezusb_set_reset(dev, fx.cpucs_reg, 1);
+	if (ret < 0)
+		goto out;
+	record = (const struct ihex_binrec *)firmware->data;
+	for (; record; record = ihex_next_binrec(record)) {
+		if (be32_to_cpu(record->addr) <= fx.max_internal_adress) {
+			ret = ezusb_writememory(dev, be32_to_cpu(record->addr),
+						(unsigned char *)record->data,
+						be16_to_cpu(record->len), WRITE_INT_RAM);
+			if (ret < 0) {
+				dev_err(&dev->dev, "%s - ezusb_writememory "
+					"failed writing external memory "
+					"(%d %04X %p %d)\n", __func__, ret,
+					be32_to_cpu(record->addr), record->data,
+					be16_to_cpu(record->len));
+				goto out;
+			}
+		}
+	}
+	ret = ezusb_set_reset(dev, fx.cpucs_reg, 0);
+out:
+	release_firmware(firmware);
+	return ret;
+}
+
+int ezusb_fx1_ihex_firmware_download(struct usb_device *dev,
+				     const char *firmware_path)
+{
+	return ezusb_ihex_firmware_download(dev, ezusb_fx1, firmware_path);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx1_ihex_firmware_download);
+
+#if 0
+/*
+ * Once someone one needs these fx2 functions, uncomment them
+ * and add them to ezusb.h and all should be good.
+ */
+static struct ezusb_fx_type ezusb_fx2 = {
+	.cpucs_reg = 0xE600,
+	.max_internal_adress = 0x3FFF,
+};
+
+int ezusb_fx2_set_reset(struct usb_device *dev, unsigned char reset_bit)
+{
+	return ezusb_set_reset(dev, ezusb_fx2.cpucs_reg, reset_bit);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx2_set_reset);
+
+int ezusb_fx2_ihex_firmware_download(struct usb_device *dev,
+				     const char *firmware_path)
+{
+	return ezusb_ihex_firmware_download(dev, ezusb_fx2, firmware_path);
+}
+EXPORT_SYMBOL_GPL(ezusb_fx2_ihex_firmware_download);
+#endif
+
+MODULE_DESCRIPTION("EZUSB device support");
+MODULE_LICENSE("GPL");