sys/linux: add basic examples of vusb variants

This change is the first step in addressing issue [1].

Despite syzkaller's best efforts, some usb drivers are proving
resistant to attempts to probe them. Specifically, crafted
devices are not accurate enough to bypass checks in probe().
These checks mostly deal with usb interfaces and endpoints.

One way to address this issue is to define syz_connect_* calls
variants to help syzkaller succeed probing by describing in detail
various device attributes.

Start by describing such calls for select drivers, each representing
its own category of sorts. At the moment, code coverage for these
drivers is unimpressive:

- rtl8150
Used to succeed probing until a better usb endpoint check was implemented.

- sierra_net
Same as rtl8150. Depends on usbnet API for bind() and usb ep checks.

- lan78xx
Requires numerous control requests between driver and device DURING probe.
Extra descriptions are helpful but are not enough to fully complete
probing process.

Also, add a seed for each such example.

This is only a stepping stone to improve usb fuzzing results and most
likely will be subject to change in the future.

[1] https://github.com/google/syzkaller/issues/6206

1 files changed, 172 insertions, 0 deletions

diff --git a/sys/linux/vusb.txt b/sys/linux/vusb.txt
index da0f1dc45..217552ac7 100644
--- a/sys/linux/vusb.txt
+++ b/sys/linux/vusb.txt
@@ -1438,3 +1438,175 @@ htc_frame_flags = HTC_FLAGS_RECV_TRAILER
 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+
+# Assorted driver-specific descriptions of generic syz_* calls' variants.
+
+# Generic calls such as syz_usb_connect() and syz_usb_control_io() should be enough
+# (in theory) to emulate a proper device and finish driver probes without a hitch.
+# However, there are cases when syzkaller fails to come up with correct inputs to achieve it.
+# Use fixed descriptors to quickly pass through probe() to access select drivers' post-probe functionality.
+
+# It is important to note that, one way or another, drivers in question require multiple control requests
+# between a driver and a device processed during probe(). Descriptions below do not deal with specific
+# CTRL requests as such (except for basic information included in vusb_responses_XXX). Instead, rely on
+# seeds, created both manually and with syzkaller's help. For examples, see sys/linux/test/vusb_XXX.
+
+# Common constants for endpoint descriptors.
+define USB_ENDPOINT_BULK_ATTR	(USB_ENDPOINT_XFER_BULK)
+define USB_ENDPOINT_INT_ATTR	(USB_ENDPOINT_XFER_INT)
+
+define USB_FIXED_ENDPOINT_BULK_IN_ADDR	(1 | USB_DIR_IN)
+define USB_FIXED_ENDPOINT_BULK_OUT_ADDR	(2)
+define USB_FIXED_ENDPOINT_INT_IN_ADDR	(3 | USB_DIR_IN)
+
+define USB_RECIP_DEVICE	0x00
+
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+
+# rtl8150 driver specific descriptions.
+
+resource fd_usb_rtl8150[fd_usb]
+
+syz_usb_connect$rtl8150(speed flags[usb_device_speed], dev_len len[dev], dev ptr[in, usb_device_descriptor_rtl8150], conn_descs const[0]) fd_usb_rtl8150 (timeout[3000], prog_timeout[3000], remote_cover)
+syz_usb_control_io$rtl8150(fd fd_usb_rtl8150, descs ptr[in, vusb_descriptors_rtl8150], resps ptr[in, vusb_responses_rtl8150]) (timeout[300], remote_cover)
+
+usb_device_descriptor_rtl8150 {
+	inner	usb_device_descriptor_fixed_t[0x200, USB_CLASS_VENDOR_SPEC, USB_SUBCLASS_VENDOR_SPEC, 0xff, 64, 0xbda, 0x8150, 0, array[usb_config_descriptor_rtl8150, 1]]
+} [packed]
+
+usb_config_descriptor_rtl8150 {
+	inner	usb_config_descriptor_fixed_t[1, 1, USB_CONFIG_ATT_ONE, 250, usb_interface_descriptor_rtl8150]
+} [packed]
+
+usb_interface_descriptor_rtl8150 {
+	iface	usb_interface_descriptor_fixed_t[0, 0, 3, USB_CLASS_VENDOR_SPEC, 0, 0, void, usb_endpoint_descriptors_rtl8150]
+} [packed]
+
+usb_endpoint_descriptors_rtl8150 {
+	bulk_in		usb_endpoint_descriptor_fixed_t[USB_FIXED_ENDPOINT_BULK_IN_ADDR, USB_ENDPOINT_BULK_ATTR, 512, 0, void]
+	bulk_out	usb_endpoint_descriptor_fixed_t[USB_FIXED_ENDPOINT_BULK_OUT_ADDR, USB_ENDPOINT_BULK_ATTR, 512, 0, void]
+	int_in		usb_endpoint_descriptor_fixed_t[USB_FIXED_ENDPOINT_INT_IN_ADDR, USB_ENDPOINT_INT_ATTR, 64, 1, void]
+} [packed]
+
+vusb_descriptors_rtl8150 {
+	len		len[parent, int32]
+	generic		ptr[in, vusb_descriptor_generic]
+
+	USB_DT_STRING	ptr[in, vusb_descriptor_t[USB_TYPE_STANDARD, USB_DT_STRING, usb_string_descriptor]]
+} [packed]
+
+vusb_responses_rtl8150 {
+	len				len[parent, int32]
+	generic				ptr[in, vusb_response_generic]
+
+	USB_REQ_GET_INTERFACE		ptr[in, vusb_response_t[USB_TYPE_STANDARD, USB_REQ_GET_INTERFACE, int8]]
+	USB_REQ_GET_CONFIGURATION	ptr[in, vusb_response_t[USB_TYPE_STANDARD, USB_REQ_GET_CONFIGURATION, int8]]
+
+	RTL8150_REQ_GET_REGS		ptr[in, vusb_response_t[RTL8150_REQT_READ, RTL8150_REQ_GET_REGS, array[int8, 0:6]]]
+	RTL8150_REQ_SET_REGS		ptr[in, vusb_response_t[RTL8150_REQT_WRITE, RTL8150_REQ_SET_REGS, array[int8, 0:6]]]
+} [packed]
+
+define RTL8150_REQ_GET_REGS	0x05
+define RTL8150_REQ_SET_REGS	0x05
+define RTL8150_REQT_READ	0xc0
+define RTL8150_REQT_WRITE	0x40
+
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+
+# sierra_net driver specific descriptions.
+
+resource fd_usb_sierra_net[fd_usb]
+
+syz_usb_connect$sierra_net(speed flags[usb_device_speed], dev_len len[dev], dev ptr[in, usb_device_descriptor_sierra_net], conn_descs const[0]) fd_usb_sierra_net (timeout[3000], prog_timeout[3000], remote_cover)
+syz_usb_control_io$sierra_net(fd fd_usb_sierra_net, descs ptr[in, vusb_descriptors_sierra_net], resps ptr[in, vusb_responses_sierra_net]) (timeout[300], remote_cover)
+
+usb_device_descriptor_sierra_net {
+	inner	usb_device_descriptor_fixed_t[0x200, USB_CLASS_VENDOR_SPEC, USB_SUBCLASS_VENDOR_SPEC, 0xff, 64, 0x1199, 0x68a3, 0, array[usb_config_descriptor_sierra_net, 1]]
+} [packed]
+
+usb_config_descriptor_sierra_net {
+	inner	usb_config_descriptor_fixed_t[1, 1, USB_CONFIG_ATT_ONE, 250, usb_interface_descriptor_sierra_net]
+} [packed]
+
+usb_interface_descriptor_sierra_net {
+	iface	usb_interface_descriptor_fixed_t[7, 0, 3, USB_CLASS_VENDOR_SPEC, 0, 0, void, usb_endpoint_descriptors_sierra_net]
+} [packed]
+
+# sierra_net driver does not expect fixed ep addresses, so refrain from being too specific here.
+# As long as we ensure there are 3 endpoints, 2 bulk and 1 int, syzkaller should figure it out.
+usb_endpoint_descriptors_sierra_net {
+	bulk_in		usb_endpoint_descriptor_t[flags[usb_endpoint_addresses, int8], const[USB_ENDPOINT_BULK_ATTR, int8], void]
+	bulk_out	usb_endpoint_descriptor_t[flags[usb_endpoint_addresses, int8], const[USB_ENDPOINT_BULK_ATTR, int8], void]
+	status		usb_endpoint_descriptor_t[flags[usb_endpoint_addresses, int8], const[USB_ENDPOINT_INT_ATTR, int8], void]
+} [packed]
+
+vusb_descriptors_sierra_net {
+	len		len[parent, int32]
+	generic		ptr[in, vusb_descriptor_generic]
+
+	USB_DT_STRING	ptr[in, vusb_descriptor_t[USB_TYPE_STANDARD, USB_DT_STRING, usb_string_descriptor]]
+} [packed]
+
+vusb_responses_sierra_net {
+	len					len[parent, int32]
+	generic					ptr[in, vusb_response_generic]
+
+	USB_CDC_GET_ENCAPSULATED_RESPONSE	ptr[in, vusb_response_t[SIERRA_CMD_TYPE_IN, USB_CDC_GET_ENCAPSULATED_RESPONSE, array[int8, 1024]]]
+	USB_CDC_SEND_ENCAPSULATED_COMMANDT	ptr[in, vusb_response_t[SIERRA_CMD_TYPE_OUT, USB_CDC_SEND_ENCAPSULATED_COMMAND, array[int8, 0:4]]]
+} [packed]
+
+define SIERRA_CMD_TYPE_IN	(USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE)
+define SIERRA_CMD_TYPE_OUT	(USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE)
+
+# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
+
+# lan78xx driver specific descriptions.
+# While these syz_* variants noticably help with the probe() process, they are not enough.
+# This is due to a high number of control requests expected between the driver and the device.
+
+include <drivers/net/usb/smsc95xx.h>
+
+resource fd_usb_lan78xx[fd_usb]
+
+syz_usb_connect$lan78xx(speed flags[usb_device_speed], dev_len len[dev], dev ptr[in, usb_device_descriptor_lan78xx], conn_descs const[0]) fd_usb_lan78xx (timeout[3000], prog_timeout[3000], remote_cover)
+syz_usb_control_io$lan78xx(fd fd_usb_lan78xx, descs ptr[in, vusb_descriptors_lan78xx], resps ptr[in, vusb_responses_lan78xx]) (timeout[300], remote_cover)
+
+usb_device_descriptor_lan78xx {
+	inner	usb_device_descriptor_fixed_t[0x200, USB_CLASS_VENDOR_SPEC, USB_SUBCLASS_VENDOR_SPEC, 0xff, 64, 0x424, 0x7850, 0, array[usb_config_descriptor_lan78xx, 1]]
+} [packed]
+
+usb_config_descriptor_lan78xx {
+	inner	usb_config_descriptor_fixed_t[1, 1, USB_CONFIG_ATT_ONE, 250, usb_interface_descriptor_lan78xx]
+} [packed]
+
+usb_interface_descriptor_lan78xx {
+	iface	usb_interface_descriptor_fixed_t[0, 0, 3, USB_CLASS_VENDOR_SPEC, 0, 0, void, usb_endpoint_descriptors_lan78xx]
+} [packed]
+
+usb_endpoint_descriptors_lan78xx {
+	bulk_in		usb_endpoint_descriptor_fixed_t[USB_FIXED_ENDPOINT_BULK_IN_ADDR, USB_ENDPOINT_BULK_ATTR, 512, 0, void]
+	bulk_out	usb_endpoint_descriptor_fixed_t[USB_FIXED_ENDPOINT_BULK_OUT_ADDR, USB_ENDPOINT_BULK_ATTR, 512, 0, void]
+	int_in		usb_endpoint_descriptor_fixed_t[USB_FIXED_ENDPOINT_INT_IN_ADDR, USB_ENDPOINT_INT_ATTR, 64, 1, void]
+} [packed]
+
+vusb_descriptors_lan78xx {
+	len		len[parent, int32]
+	generic		ptr[in, vusb_descriptor_generic]
+
+	USB_DT_STRING	ptr[in, vusb_descriptor_t[USB_TYPE_STANDARD, USB_DT_STRING, usb_string_descriptor]]
+} [packed]
+
+vusb_responses_lan78xx {
+	len					len[parent, int32]
+	generic					ptr[in, vusb_response_generic]
+
+	USB_REQ_GET_INTERFACE			ptr[in, vusb_response_t[USB_TYPE_STANDARD, USB_REQ_GET_INTERFACE, int8]]
+	USB_REQ_GET_CONFIGURATION		ptr[in, vusb_response_t[USB_TYPE_STANDARD, USB_REQ_GET_CONFIGURATION, int8]]
+
+	USB_VENDOR_REQUEST_READ_REGISTER	ptr[in, vusb_response_t[LAN78XX_REG_TYPE_IN, USB_VENDOR_REQUEST_READ_REGISTER, int32]]
+	USB_VENDOR_REQUEST_WRITE_REGISTER	ptr[in, vusb_response_t[LAN78XX_REG_TYPE_OUT, USB_VENDOR_REQUEST_WRITE_REGISTER, int32]]
+	USB_VENDOR_REQUEST_GET_STATS		ptr[in, vusb_response_t[LAN78XX_REG_TYPE_IN, USB_VENDOR_REQUEST_GET_STATS, array[int8, 47]]]
+} [packed]
+
+define LAN78XX_REG_TYPE_IN	(USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE)
+define LAN78XX_REG_TYPE_OUT	(USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE)