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10164c2ad6
Fix driver new_id sysfs-attribute removal deadlock by making sure to not hold any locks that the attribute operations grab when removing the attribute. Specifically, usb_serial_deregister holds the table mutex when deregistering the driver, which includes removing the new_id attribute. This can lead to a deadlock as writing to new_id increments the attribute's active count before trying to grab the same mutex in usb_serial_probe. The deadlock can easily be triggered by inserting a sleep in usb_serial_deregister and writing the id of an unbound device to new_id during module unload. As the table mutex (in this case) is used to prevent subdriver unload during probe, it should be sufficient to only hold the lock while manipulating the usb-serial driver list during deregister. A racing probe will then either fail to find a matching subdriver or fail to get the corresponding module reference. Since v3.15-rc1 this also triggers the following lockdep warning: ====================================================== [ INFO: possible circular locking dependency detected ] 3.15.0-rc2 #123 Tainted: G W ------------------------------------------------------- modprobe/190 is trying to acquire lock: (s_active#4){++++.+}, at: [<c0167aa0>] kernfs_remove_by_name_ns+0x4c/0x94 but task is already holding lock: (table_lock){+.+.+.}, at: [<bf004d84>] usb_serial_deregister+0x3c/0x78 [usbserial] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (table_lock){+.+.+.}: [<c0075f84>] __lock_acquire+0x1694/0x1ce4 [<c0076de8>] lock_acquire+0xb4/0x154 [<c03af3cc>] _raw_spin_lock+0x4c/0x5c [<c02bbc24>] usb_store_new_id+0x14c/0x1ac [<bf007eb4>] new_id_store+0x68/0x70 [usbserial] [<c025f568>] drv_attr_store+0x30/0x3c [<c01690e0>] sysfs_kf_write+0x5c/0x60 [<c01682c0>] kernfs_fop_write+0xd4/0x194 [<c010881c>] vfs_write+0xbc/0x198 [<c0108e4c>] SyS_write+0x4c/0xa0 [<c000f880>] ret_fast_syscall+0x0/0x48 -> #0 (s_active#4){++++.+}: [<c03a7a28>] print_circular_bug+0x68/0x2f8 [<c0076218>] __lock_acquire+0x1928/0x1ce4 [<c0076de8>] lock_acquire+0xb4/0x154 [<c0166b70>] __kernfs_remove+0x254/0x310 [<c0167aa0>] kernfs_remove_by_name_ns+0x4c/0x94 [<c0169fb8>] remove_files.isra.1+0x48/0x84 [<c016a2fc>] sysfs_remove_group+0x58/0xac [<c016a414>] sysfs_remove_groups+0x34/0x44 [<c02623b8>] driver_remove_groups+0x1c/0x20 [<c0260e9c>] bus_remove_driver+0x3c/0xe4 [<c026235c>] driver_unregister+0x38/0x58 [<bf007fb4>] usb_serial_bus_deregister+0x84/0x88 [usbserial] [<bf004db4>] usb_serial_deregister+0x6c/0x78 [usbserial] [<bf005330>] usb_serial_deregister_drivers+0x2c/0x4c [usbserial] [<bf016618>] usb_serial_module_exit+0x14/0x1c [sierra] [<c009d6cc>] SyS_delete_module+0x184/0x210 [<c000f880>] ret_fast_syscall+0x0/0x48 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(table_lock); lock(s_active#4); lock(table_lock); lock(s_active#4); *** DEADLOCK *** 1 lock held by modprobe/190: #0: (table_lock){+.+.+.}, at: [<bf004d84>] usb_serial_deregister+0x3c/0x78 [usbserial] stack backtrace: CPU: 0 PID: 190 Comm: modprobe Tainted: G W 3.15.0-rc2 #123 [<c0015e10>] (unwind_backtrace) from [<c0013728>] (show_stack+0x20/0x24) [<c0013728>] (show_stack) from [<c03a9a54>] (dump_stack+0x24/0x28) [<c03a9a54>] (dump_stack) from [<c03a7cac>] (print_circular_bug+0x2ec/0x2f8) [<c03a7cac>] (print_circular_bug) from [<c0076218>] (__lock_acquire+0x1928/0x1ce4) [<c0076218>] (__lock_acquire) from [<c0076de8>] (lock_acquire+0xb4/0x154) [<c0076de8>] (lock_acquire) from [<c0166b70>] (__kernfs_remove+0x254/0x310) [<c0166b70>] (__kernfs_remove) from [<c0167aa0>] (kernfs_remove_by_name_ns+0x4c/0x94) [<c0167aa0>] (kernfs_remove_by_name_ns) from [<c0169fb8>] (remove_files.isra.1+0x48/0x84) [<c0169fb8>] (remove_files.isra.1) from [<c016a2fc>] (sysfs_remove_group+0x58/0xac) [<c016a2fc>] (sysfs_remove_group) from [<c016a414>] (sysfs_remove_groups+0x34/0x44) [<c016a414>] (sysfs_remove_groups) from [<c02623b8>] (driver_remove_groups+0x1c/0x20) [<c02623b8>] (driver_remove_groups) from [<c0260e9c>] (bus_remove_driver+0x3c/0xe4) [<c0260e9c>] (bus_remove_driver) from [<c026235c>] (driver_unregister+0x38/0x58) [<c026235c>] (driver_unregister) from [<bf007fb4>] (usb_serial_bus_deregister+0x84/0x88 [usbserial]) [<bf007fb4>] (usb_serial_bus_deregister [usbserial]) from [<bf004db4>] (usb_serial_deregister+0x6c/0x78 [usbserial]) [<bf004db4>] (usb_serial_deregister [usbserial]) from [<bf005330>] (usb_serial_deregister_drivers+0x2c/0x4c [usbserial]) [<bf005330>] (usb_serial_deregister_drivers [usbserial]) from [<bf016618>] (usb_serial_module_exit+0x14/0x1c [sierra]) [<bf016618>] (usb_serial_module_exit [sierra]) from [<c009d6cc>] (SyS_delete_module+0x184/0x210) [<c009d6cc>] (SyS_delete_module) from [<c000f880>] (ret_fast_syscall+0x0/0x48) Signed-off-by: Johan Hovold <jhovold@gmail.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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.. | ||
atm | ||
c67x00 | ||
chipidea | ||
class | ||
core | ||
dwc2 | ||
dwc3 | ||
early | ||
gadget | ||
host | ||
image | ||
misc | ||
mon | ||
musb | ||
phy | ||
renesas_usbhs | ||
serial | ||
storage | ||
wusbcore | ||
Kconfig | ||
Makefile | ||
README | ||
usb-common.c | ||
usb-skeleton.c |
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 ("khubd"). 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.