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, 218 insertions, 0 deletions

diff --git a/drivers/usb/atm/xusbatm.c b/drivers/usb/atm/xusbatm.c
new file mode 100644
index 000000000..5c1e1f521
--- /dev/null
+++ b/drivers/usb/atm/xusbatm.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0+
+/******************************************************************************
+ *  xusbatm.c -	dumb usbatm-based driver for modems initialized in userspace
+ *
+ *  Copyright (C) 2005 Duncan Sands, Roman Kagan (rkagan % mail ! ru)
+ ******************************************************************************/
+
+#include <linux/module.h>
+#include <linux/etherdevice.h>		/* for eth_random_addr() */
+
+#include "usbatm.h"
+
+
+#define XUSBATM_DRIVERS_MAX	8
+
+#define XUSBATM_PARM(name, type, parmtype, desc) \
+	static type name[XUSBATM_DRIVERS_MAX]; \
+	static unsigned int num_##name; \
+	module_param_array(name, parmtype, &num_##name, 0444); \
+	MODULE_PARM_DESC(name, desc)
+
+XUSBATM_PARM(vendor, unsigned short, ushort, "USB device vendor");
+XUSBATM_PARM(product, unsigned short, ushort, "USB device product");
+
+XUSBATM_PARM(rx_endpoint, unsigned char, byte, "rx endpoint number");
+XUSBATM_PARM(tx_endpoint, unsigned char, byte, "tx endpoint number");
+XUSBATM_PARM(rx_padding, unsigned char, byte, "rx padding (default 0)");
+XUSBATM_PARM(tx_padding, unsigned char, byte, "tx padding (default 0)");
+XUSBATM_PARM(rx_altsetting, unsigned char, byte, "rx altsetting (default 0)");
+XUSBATM_PARM(tx_altsetting, unsigned char, byte, "rx altsetting (default 0)");
+
+static const char xusbatm_driver_name[] = "xusbatm";
+
+static struct usbatm_driver xusbatm_drivers[XUSBATM_DRIVERS_MAX];
+static struct usb_device_id xusbatm_usb_ids[XUSBATM_DRIVERS_MAX + 1];
+static struct usb_driver xusbatm_usb_driver;
+
+static struct usb_interface *xusbatm_find_intf(struct usb_device *usb_dev, int altsetting, u8 ep)
+{
+	struct usb_host_interface *alt;
+	struct usb_interface *intf;
+	int i, j;
+
+	for (i = 0; i < usb_dev->actconfig->desc.bNumInterfaces; i++)
+		if ((intf = usb_dev->actconfig->interface[i]) && (alt = usb_altnum_to_altsetting(intf, altsetting)))
+			for (j = 0; j < alt->desc.bNumEndpoints; j++)
+				if (alt->endpoint[j].desc.bEndpointAddress == ep)
+					return intf;
+	return NULL;
+}
+
+static int xusbatm_capture_intf(struct usbatm_data *usbatm, struct usb_device *usb_dev,
+		struct usb_interface *intf, int altsetting, int claim)
+{
+	int ifnum = intf->altsetting->desc.bInterfaceNumber;
+	int ret;
+
+	if (claim && (ret = usb_driver_claim_interface(&xusbatm_usb_driver, intf, usbatm))) {
+		usb_err(usbatm, "%s: failed to claim interface %2d (%d)!\n", __func__, ifnum, ret);
+		return ret;
+	}
+	ret = usb_set_interface(usb_dev, ifnum, altsetting);
+	if (ret) {
+		usb_err(usbatm, "%s: altsetting %2d for interface %2d failed (%d)!\n", __func__, altsetting, ifnum, ret);
+		return ret;
+	}
+	return 0;
+}
+
+static void xusbatm_release_intf(struct usb_device *usb_dev, struct usb_interface *intf, int claimed)
+{
+	if (claimed) {
+		usb_set_intfdata(intf, NULL);
+		usb_driver_release_interface(&xusbatm_usb_driver, intf);
+	}
+}
+
+static int xusbatm_bind(struct usbatm_data *usbatm,
+			struct usb_interface *intf, const struct usb_device_id *id)
+{
+	struct usb_device *usb_dev = interface_to_usbdev(intf);
+	int drv_ix = id->driver_info;
+	int rx_alt = rx_altsetting[drv_ix];
+	int tx_alt = tx_altsetting[drv_ix];
+	struct usb_interface *rx_intf = xusbatm_find_intf(usb_dev, rx_alt, rx_endpoint[drv_ix]);
+	struct usb_interface *tx_intf = xusbatm_find_intf(usb_dev, tx_alt, tx_endpoint[drv_ix]);
+	int ret;
+
+	usb_dbg(usbatm, "%s: binding driver %d: vendor %04x product %04x"
+		" rx: ep %02x padd %d alt %2d tx: ep %02x padd %d alt %2d\n",
+		__func__, drv_ix, vendor[drv_ix], product[drv_ix],
+		rx_endpoint[drv_ix], rx_padding[drv_ix], rx_alt,
+		tx_endpoint[drv_ix], tx_padding[drv_ix], tx_alt);
+
+	if (!rx_intf || !tx_intf) {
+		if (!rx_intf)
+			usb_dbg(usbatm, "%s: no interface contains endpoint %02x in altsetting %2d\n",
+				__func__, rx_endpoint[drv_ix], rx_alt);
+		if (!tx_intf)
+			usb_dbg(usbatm, "%s: no interface contains endpoint %02x in altsetting %2d\n",
+				__func__, tx_endpoint[drv_ix], tx_alt);
+		return -ENODEV;
+	}
+
+	if ((rx_intf != intf) && (tx_intf != intf))
+		return -ENODEV;
+
+	if ((rx_intf == tx_intf) && (rx_alt != tx_alt)) {
+		usb_err(usbatm, "%s: altsettings clash on interface %2d (%2d vs %2d)!\n", __func__,
+				rx_intf->altsetting->desc.bInterfaceNumber, rx_alt, tx_alt);
+		return -EINVAL;
+	}
+
+	usb_dbg(usbatm, "%s: rx If#=%2d; tx If#=%2d\n", __func__,
+			rx_intf->altsetting->desc.bInterfaceNumber,
+			tx_intf->altsetting->desc.bInterfaceNumber);
+
+	ret = xusbatm_capture_intf(usbatm, usb_dev, rx_intf, rx_alt, rx_intf != intf);
+	if (ret)
+		return ret;
+
+	if ((tx_intf != rx_intf) && (ret = xusbatm_capture_intf(usbatm, usb_dev, tx_intf, tx_alt, tx_intf != intf))) {
+		xusbatm_release_intf(usb_dev, rx_intf, rx_intf != intf);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void xusbatm_unbind(struct usbatm_data *usbatm,
+			   struct usb_interface *intf)
+{
+	struct usb_device *usb_dev = interface_to_usbdev(intf);
+	int i;
+
+	usb_dbg(usbatm, "%s entered\n", __func__);
+
+	for (i = 0; i < usb_dev->actconfig->desc.bNumInterfaces; i++) {
+		struct usb_interface *cur_intf = usb_dev->actconfig->interface[i];
+
+		if (cur_intf && (usb_get_intfdata(cur_intf) == usbatm)) {
+			usb_set_intfdata(cur_intf, NULL);
+			usb_driver_release_interface(&xusbatm_usb_driver, cur_intf);
+		}
+	}
+}
+
+static int xusbatm_atm_start(struct usbatm_data *usbatm,
+			     struct atm_dev *atm_dev)
+{
+	atm_dbg(usbatm, "%s entered\n", __func__);
+
+	/* use random MAC as we've no way to get it from the device */
+	eth_random_addr(atm_dev->esi);
+
+	return 0;
+}
+
+
+static int xusbatm_usb_probe(struct usb_interface *intf,
+			     const struct usb_device_id *id)
+{
+	return usbatm_usb_probe(intf, id,
+				xusbatm_drivers + (id - xusbatm_usb_ids));
+}
+
+static struct usb_driver xusbatm_usb_driver = {
+	.name		= xusbatm_driver_name,
+	.probe		= xusbatm_usb_probe,
+	.disconnect	= usbatm_usb_disconnect,
+	.id_table	= xusbatm_usb_ids,
+	.no_dynamic_id	= 1,
+};
+
+static int __init xusbatm_init(void)
+{
+	int i;
+
+	if (!num_vendor ||
+	    num_vendor != num_product ||
+	    num_vendor != num_rx_endpoint ||
+	    num_vendor != num_tx_endpoint) {
+		pr_warn("xusbatm: malformed module parameters\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < num_vendor; i++) {
+		rx_endpoint[i] |= USB_DIR_IN;
+		tx_endpoint[i] &= USB_ENDPOINT_NUMBER_MASK;
+
+		xusbatm_usb_ids[i].match_flags	= USB_DEVICE_ID_MATCH_DEVICE;
+		xusbatm_usb_ids[i].idVendor	= vendor[i];
+		xusbatm_usb_ids[i].idProduct	= product[i];
+		xusbatm_usb_ids[i].driver_info	= i;
+
+		xusbatm_drivers[i].driver_name	= xusbatm_driver_name;
+		xusbatm_drivers[i].bind		= xusbatm_bind;
+		xusbatm_drivers[i].unbind	= xusbatm_unbind;
+		xusbatm_drivers[i].atm_start	= xusbatm_atm_start;
+		xusbatm_drivers[i].bulk_in	= rx_endpoint[i];
+		xusbatm_drivers[i].bulk_out	= tx_endpoint[i];
+		xusbatm_drivers[i].rx_padding	= rx_padding[i];
+		xusbatm_drivers[i].tx_padding	= tx_padding[i];
+	}
+
+	return usb_register(&xusbatm_usb_driver);
+}
+module_init(xusbatm_init);
+
+static void __exit xusbatm_exit(void)
+{
+	usb_deregister(&xusbatm_usb_driver);
+}
+module_exit(xusbatm_exit);
+
+MODULE_AUTHOR("Roman Kagan, Duncan Sands");
+MODULE_DESCRIPTION("Driver for USB ADSL modems initialized in userspace");
+MODULE_LICENSE("GPL");