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[ Upstream commit a2cf936ebef291ef7395172b9e2f624779fb6dc0 ] This prevents use of a stale pointer if functions are called after g_cleanup that shouldn't be. This doesn't fix any races, but converts a possibly silent kernel memory corruption into an obvious NULL pointer dereference report. Fixes: eb9fecb9e69b ("usb: gadget: f_uac2: split out audio core") Signed-off-by: Chris Wulff <chris.wulff@biamp.com> Link: https://lore.kernel.org/stable/CO1PR17MB54194226DA08BFC9EBD8C163E1172%40CO1PR17MB5419.namprd17.prod.outlook.com Link: https://lore.kernel.org/r/CO1PR17MB54194226DA08BFC9EBD8C163E1172@CO1PR17MB5419.namprd17.prod.outlook.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> (cherry picked from commit a646645af00f65db78fe4a60f753f2b07df35b6e) Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
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.