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

3 files changed, 118 insertions, 0 deletions

diff --git a/sys/linux/test/vusb_lan78xx b/sys/linux/test/vusb_lan78xx
new file mode 100644
index 000000000..461ff4825
--- /dev/null
+++ b/sys/linux/test/vusb_lan78xx
@@ -0,0 +1,72 @@
+# This seed helps syzkaller to reliably pass the probe() checks for lan78xx driver.
+# As some CTRL requests occur during the probe, a few syz_usb_control_io() calls may
+# be in a weird order or even duplicate.
+
+# TODO: currently, probe does not succeed completely. Most likely, it stems from the fact that
+# the abundance of expected CTRL requests *during* probe is not something syzkaller can handle at the moment.
+# Timing is essential among other things. This should be mitigated by a separate syz_usb_connect pseudo-call 
+# that deals with such requests without syz_usb_control_io.
+
+# Ensure that we pass driver-specific basic usb interface and endpoint checks during initial probe() stages.
+
+r0 = syz_usb_connect$lan78xx(0x5, 0x3f, &(0x7f0000000000)={{0x12, 0x1, 0x200, 0xff, 0xff, 0xff, 0x40, 0x424, 0x7850, 0x0, 0x1, 0x2, 0x3, 0x1, [{{0x9, 0x2, 0x2d, 0x1, 0x1, 0x0, 0x80, 0xfa, {{0x9, 0x4, 0x0, 0x0, 0x3, 0xff, 0x0, 0x0, 0x0, "", {{0x9, 0x5, 0x81, 0x2, 0x200, 0x0, 0x0, 0x0, ""}, {0x9, 0x5, 0x2, 0x2, 0x200, 0x0, 0x0, 0x0, ""}, {0x9, 0x5, 0x83, 0x3, 0x40, 0x1, 0x0, 0x0, ""}}}}}}]}}, 0x0)
+
+# This is where the fun begins.
+# Functions like lan78xx_bind() and lan78xx_phy_init() in lan78xx_probe() utilize ~50 CTRL requests, both directions, during probe.
+
+# Write to INT_EP_CTL register in lan78xx_setup_irq_domain().
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f00000003c0)={0x34, &(0x7f0000000140)={0x20, 0x11, 0x0, ""}, 0x0, 0x0, 0x0, 0x0, 0x0})
+
+# Write to HW_CFG register in lan78xx_reset().
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f0000000780)={0x34, &(0x7f0000000600)={0x40, 0x11, 0x0, ""}, 0x0, 0x0, 0x0, 0x0, 0x0})
+
+# Read from HW_CFG register.
+
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+
+# Write to HW_CFG register.
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f0000000f00)={0x34, &(0x7f0000000cc0)={0x40, 0x10, 0x0, ""}, 0x0, 0x0, 0x0, 0x0, 0x0})
+
+# Write to RX_ADDRL and RX_ADDRH registers in lan78xx_init_mac_address().
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f0000001240)={0x34, &(0x7f0000001080)={0x0, 0x6, 0x0, ""}, 0x0, 0x0, 0x0, 0x0, 0x0})
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f0000001700)={0x34, &(0x7f0000001500)={0x20, 0x18, 0x1, ')'}, 0x0, 0x0, 0x0, 0x0, 0x0})
+
+# Read from MAF_LO(0) and MAF_HI(0) registers.
+
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+
+# Write to ID_REV register, back in lan78xx_reset().
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f0000002180)={0x34, &(0x7f0000000400)=ANY=[], 0x0, 0x0, 0x0, 0x0, 0x0})
+
+# Write and read to/from USB_CFG0 register.
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f00000006c0)={0x34, &(0x7f0000000500)={0x0, 0x7, 0x0, ""}, 0x0, 0x0, 0x0, 0x0, 0x0})
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+
+# Write to USB_CFG1 register in lan78xx_init_ltm().
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f0000002540)={0x34, &(0x7f0000002340)={0x0, 0xf, 0x0, ""}, 0x0, 0x0, 0x0, 0x0, 0x0})
+
+# Read from 6 registers (LTM_BELT_IDLE0 etc.) in a row.
+
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+
+# Read from BURST_CAP and BULK_IN_DLY registers in lan78xx_reset().
+
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+syz_usb_control_io$lan78xx(r0, 0x0, 0x0)
+
+# Write to HW_CFG register.
+
+syz_usb_control_io$lan78xx(r0, 0x0, &(0x7f0000000380)={0x34, &(0x7f0000000840)={0x0, 0x0, 0x0, ""}, 0x0, 0x0, 0x0, 0x0, 0x0})
diff --git a/sys/linux/test/vusb_rtl8150 b/sys/linux/test/vusb_rtl8150
new file mode 100644
index 000000000..6f8accf7c
--- /dev/null
+++ b/sys/linux/test/vusb_rtl8150
@@ -0,0 +1,25 @@
+# This seed helps syzkaller to reliably pass the probe() checks for rtl8150 driver.
+# As some CTRL requests occur during the probe, a few syz_usb_control_io() calls may
+# be in a weird order or even duplicate.
+
+# Ensure that we pass driver-specific basic usb interface and endpoint checks during initial probe() stages.
+
+r0 = syz_usb_connect$rtl8150(0x3, 0x3f, &(0x7f00000003c0)={{0x12, 0x1, 0x110, 0xff, 0xff, 0x0, 0x40, 0xbda, 0x8150, 0x40, 0x1, 0x2, 0x3, 0x1, [{{0x9, 0x2, 0x2d, 0x1, 0x1, 0x5, 0x80, 0x0, {{0x9, 0x4, 0x0, 0x7f, 0x3, 0xff, 0x11, 0x1, 0x5, "", {{0x9, 0x5, 0x81, 0x2, 0x40, 0x6, 0x9, 0x4, ""}, {0x9, 0x5, 0x2, 0x2, 0x20, 0x2, 0x57, 0x6e, ""}, {0x9, 0x5, 0x83, 0x3, 0x240, 0x3, 0x82, 0x8, ""}}}}}}]}}, 0x0)
+
+# During probe, rtl8150_reset() requires reading/writing registers via usb_control_msg(), see:
+# https://elixir.bootlin.com/linux/v6.16/source/drivers/net/usb/rtl8150.c#L316
+
+# The timing of dealing with CTRL requests is very awkward. So as not to fail dealing with registers, these calls come in.
+# They are not directly related to rtl8150 code itself yet seem to be making that the next calls below run on time.
+# TODO: figure out the circumstances fully and consider switching to sleep/nanosleep instead.
+
+syz_usb_control_io$rtl8150(r0, &(0x7f0000000580)={0x14, 0x0, &(0x7f0000000480)={0x0, 0x3, 0x3, @lang_id={0x0, 0x3, 0x0}}}, 0x0)
+syz_usb_control_io$rtl8150(r0, &(0x7f0000002980)={0x14, 0x0, &(0x7f00000028c0)={0x0, 0x3, 0x3, @lang_id={0x0, 0x3, 0x0}}}, 0x0)
+
+# Receive a request via set_registers().
+
+syz_usb_control_io$rtl8150(r0, 0x0, 0x0)
+
+# Send a request via get_registers(). Sent data should make the while{} loop in rtl8150_reset() stop early.
+
+syz_usb_control_io$rtl8150(r0, 0x0, &(0x7f0000004280)={0x2c, 0x0, 0x0, 0x0, 0x0, &(0x7f0000004240)={0x40, 0x5, 0x2, "2bd8"}})
diff --git a/sys/linux/test/vusb_sierra_net b/sys/linux/test/vusb_sierra_net
new file mode 100644
index 000000000..482f7619f
--- /dev/null
+++ b/sys/linux/test/vusb_sierra_net
@@ -0,0 +1,21 @@
+# This seed helps syzkaller to reliably pass the probe() checks for sierra_net driver.
+# As some CTRL requests occur during the probe, a few syz_usb_control_io() calls may
+# be in a weird order or even duplicate.
+
+# Ensure that we pass driver-specific basic usb interface and endpoint checks during initial probe() stages.
+
+r0 = syz_usb_connect$sierra_net(0x0, 0x3f, &(0x7f0000000080)={{0x12, 0x1, 0x200, 0xff, 0xff, 0xff, 0x40, 0x1199, 0x68a3, 0x0, 0x1, 0x2, 0x3, 0x1, [{{0x9, 0x2, 0x2d, 0x1, 0x1, 0x0, 0x80, 0xfa, {{0x9, 0x4, 0x7, 0x0, 0x3, 0xff, 0x0, 0x0, 0x0, "", {{0x9, 0x5, 0x43978451d8f6fedb, 0x2, 0x40, 0x2, 0x1b, 0xfe, ""}, {0x9, 0x5, 0x7, 0x2, 0x200, 0xc, 0x77, 0x3, ""}, {0x9, 0x5, 0x81, 0x3, 0x20, 0x0, 0xfd, 0x32, ""}}}}}}]}}, 0x0)
+
+# To pass the probe, at the minumum one has to make the crafted device write to the driver in sierra_net_get_fw_attr(), see:
+# https://elixir.bootlin.com/linux/v6.16/source/drivers/net/usb/sierra_net.c#L636
+# Technically, there are other CTRL requests, such as the ones in sierra_net_dosync() - however, they are allowed to fail, so we can ignore them.
+
+# Seemingly, this call is only here to keep the timing right. 
+# TODO: fix the expected delay with sleep/nanosleep.
+
+syz_usb_control_io$sierra_net(r0, 0x0, 0x0)
+
+# Send a CTRL request to driver concerning firmware data. See:
+# https://elixir.bootlin.com/linux/v6.16/source/drivers/net/usb/sierra_net.c#L743
+
+syz_usb_control_io$sierra_net(r0, &(0x7f0000000100)={0x14, &(0x7f0000000000)={0x20, 0x21, 0x8, {0x8, 0x11, "e4ff14eca81f"}}, 0x0}, 0x0)