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[ Upstream commit3120aac6d0] UDC driver should not touch gadget's driver internals, especially it should not reset driver->bus. This wasn't harmful so far, but since commitfc274c1e99("USB: gadget: Add a new bus for gadgets") gadget subsystem got it's own bus and messing with ->bus triggers the following NULL pointer dereference: dwc2 12480000.hsotg: bound driver g_ether 8<--- cut here --- Unable to handle kernel NULL pointer dereference at virtual address 00000000 [00000000] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: ... CPU: 0 PID: 620 Comm: modprobe Not tainted 5.18.0-rc5-next-20220504 #11862 Hardware name: Samsung Exynos (Flattened Device Tree) PC is at module_add_driver+0x44/0xe8 LR is at sysfs_do_create_link_sd+0x84/0xe0 ... Process modprobe (pid: 620, stack limit = 0x(ptrval)) ... module_add_driver from bus_add_driver+0xf4/0x1e4 bus_add_driver from driver_register+0x78/0x10c driver_register from usb_gadget_register_driver_owner+0x40/0xb4 usb_gadget_register_driver_owner from do_one_initcall+0x44/0x1e0 do_one_initcall from do_init_module+0x44/0x1c8 do_init_module from load_module+0x19b8/0x1b9c load_module from sys_finit_module+0xdc/0xfc sys_finit_module from ret_fast_syscall+0x0/0x54 Exception stack(0xf1771fa8 to 0xf1771ff0) ... dwc2 12480000.hsotg: new device is high-speed ---[ end trace 0000000000000000 ]--- Fix this by removing driver->bus entry reset. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Link: https://lore.kernel.org/r/20220505104618.22729-1-m.szyprowski@samsung.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("hub_wq").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.