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, 177 insertions, 0 deletions

diff --git a/drivers/usb/serial/omninet.c b/drivers/usb/serial/omninet.c
new file mode 100644
index 000000000..363b8432c
--- /dev/null
+++ b/drivers/usb/serial/omninet.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB ZyXEL omni.net driver
+ *
+ * Copyright (C) 2013,2017 Johan Hovold <johan@kernel.org>
+ *
+ * See Documentation/usb/usb-serial.rst for more information on using this
+ * driver
+ *
+ * Please report both successes and troubles to the author at omninet@kroah.com
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define DRIVER_AUTHOR "Alessandro Zummo"
+#define DRIVER_DESC "USB ZyXEL omni.net Driver"
+
+#define ZYXEL_VENDOR_ID		0x0586
+#define ZYXEL_OMNINET_ID	0x1000
+#define ZYXEL_OMNI_56K_PLUS_ID	0x1500
+/* This one seems to be a re-branded ZyXEL device */
+#define BT_IGNITIONPRO_ID	0x2000
+
+#define OMNINET_HEADERLEN	4
+#define OMNINET_BULKOUTSIZE	64
+#define OMNINET_PAYLOADSIZE	(OMNINET_BULKOUTSIZE - OMNINET_HEADERLEN)
+
+/* function prototypes */
+static void omninet_process_read_urb(struct urb *urb);
+static int omninet_prepare_write_buffer(struct usb_serial_port *port,
+				void *buf, size_t count);
+static int omninet_calc_num_ports(struct usb_serial *serial,
+				struct usb_serial_endpoints *epds);
+static int omninet_port_probe(struct usb_serial_port *port);
+static void omninet_port_remove(struct usb_serial_port *port);
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(ZYXEL_VENDOR_ID, ZYXEL_OMNINET_ID) },
+	{ USB_DEVICE(ZYXEL_VENDOR_ID, ZYXEL_OMNI_56K_PLUS_ID) },
+	{ USB_DEVICE(ZYXEL_VENDOR_ID, BT_IGNITIONPRO_ID) },
+	{ }						/* Terminating entry */
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+static struct usb_serial_driver zyxel_omninet_device = {
+	.driver = {
+		.name =		"omninet",
+	},
+	.description =		"ZyXEL - omni.net usb",
+	.id_table =		id_table,
+	.num_bulk_out =		2,
+	.bulk_out_size =	OMNINET_BULKOUTSIZE,
+	.calc_num_ports =	omninet_calc_num_ports,
+	.port_probe =		omninet_port_probe,
+	.port_remove =		omninet_port_remove,
+	.process_read_urb =	omninet_process_read_urb,
+	.prepare_write_buffer =	omninet_prepare_write_buffer,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&zyxel_omninet_device, NULL
+};
+
+
+/*
+ * The protocol.
+ *
+ * The omni.net always exchange 64 bytes of data with the host. The first
+ * four bytes are the control header.
+ *
+ * oh_seq is a sequence number. Don't know if/how it's used.
+ * oh_len is the length of the data bytes in the packet.
+ * oh_xxx Bit-mapped, related to handshaking and status info.
+ *	I normally set it to 0x03 in transmitted frames.
+ *	7: Active when the TA is in a CONNECTed state.
+ *	6: unknown
+ *	5: handshaking, unknown
+ *	4: handshaking, unknown
+ *	3: unknown, usually 0
+ *	2: unknown, usually 0
+ *	1: handshaking, unknown, usually set to 1 in transmitted frames
+ *	0: handshaking, unknown, usually set to 1 in transmitted frames
+ * oh_pad Probably a pad byte.
+ *
+ * After the header you will find data bytes if oh_len was greater than zero.
+ */
+struct omninet_header {
+	__u8	oh_seq;
+	__u8	oh_len;
+	__u8	oh_xxx;
+	__u8	oh_pad;
+};
+
+struct omninet_data {
+	__u8	od_outseq;	/* Sequence number for bulk_out URBs */
+};
+
+static int omninet_calc_num_ports(struct usb_serial *serial,
+					struct usb_serial_endpoints *epds)
+{
+	/* We need only the second bulk-out for our single-port device. */
+	epds->bulk_out[0] = epds->bulk_out[1];
+	epds->num_bulk_out = 1;
+
+	return 1;
+}
+
+static int omninet_port_probe(struct usb_serial_port *port)
+{
+	struct omninet_data *od;
+
+	od = kzalloc_obj(*od);
+	if (!od)
+		return -ENOMEM;
+
+	usb_set_serial_port_data(port, od);
+
+	return 0;
+}
+
+static void omninet_port_remove(struct usb_serial_port *port)
+{
+	struct omninet_data *od;
+
+	od = usb_get_serial_port_data(port);
+	kfree(od);
+}
+
+static void omninet_process_read_urb(struct urb *urb)
+{
+	struct usb_serial_port *port = urb->context;
+	const struct omninet_header *hdr = urb->transfer_buffer;
+	const unsigned char *data;
+	size_t data_len;
+
+	if (urb->actual_length <= OMNINET_HEADERLEN || !hdr->oh_len)
+		return;
+
+	data = (char *)urb->transfer_buffer + OMNINET_HEADERLEN;
+	data_len = min_t(size_t, urb->actual_length - OMNINET_HEADERLEN,
+								hdr->oh_len);
+	tty_insert_flip_string(&port->port, data, data_len);
+	tty_flip_buffer_push(&port->port);
+}
+
+static int omninet_prepare_write_buffer(struct usb_serial_port *port,
+					void *buf, size_t count)
+{
+	struct omninet_data *od = usb_get_serial_port_data(port);
+	struct omninet_header *header = buf;
+
+	count = min_t(size_t, count, OMNINET_PAYLOADSIZE);
+
+	count = kfifo_out_locked(&port->write_fifo, buf + OMNINET_HEADERLEN,
+			count, &port->lock);
+
+	header->oh_seq = od->od_outseq++;
+	header->oh_len = count;
+	header->oh_xxx = 0x03;
+	header->oh_pad = 0x00;
+
+	/* always 64 bytes */
+	return OMNINET_BULKOUTSIZE;
+}
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL v2");