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linux/drivers/usb/gadget
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Uttkarsh Aggarwal 704842c97a usb: gadget: f_fs: Add unbind event before functionfs_unbind 
commit efb6b53520 upstream.

While exercising the unbind path, with the current implementation
the functionfs_unbind would be calling which waits for the ffs->mutex
to be available, however within the same time ffs_ep0_read is invoked
& if no setup packets are pending, it will invoke function
wait_event_interruptible_exclusive_locked_irq which by definition waits
for the ev.count to be increased inside the same mutex for which
functionfs_unbind is waiting.
This creates deadlock situation because the functionfs_unbind won't
get the lock until ev.count is increased which can only happen if
the caller ffs_func_unbind can proceed further.

Following is the illustration:

	CPU1				CPU2

ffs_func_unbind()		ffs_ep0_read()
				mutex_lock(ffs->mutex)
				wait_event(ffs->ev.count)
functionfs_unbind()
  mutex_lock(ffs->mutex)
  mutex_unlock(ffs->mutex)

ffs_event_add()

<deadlock>

Fix this by moving the event unbind before functionfs_unbind
to ensure the ev.count is incrased properly.

Fixes: 6a19da1110 ("usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait")
Cc: stable <stable@kernel.org>
Signed-off-by: Uttkarsh Aggarwal <quic_uaggarwa@quicinc.com>
Link: https://lore.kernel.org/r/20230525092854.7992-1-quic_uaggarwa@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2023-06-09 10:34:20 +02:00
..
function usb: gadget: f_fs: Add unbind event before functionfs_unbind 2023-06-09 10:34:20 +02:00
legacy usb: gadget: g_webcam: Send color matching descriptor per frame 2023-01-24 07:24:38 +01:00
udc Revert "usb: gadget: udc: core: Invoke usb_gadget_connect only when started" 2023-05-24 17:32:49 +01:00
composite.c USB: gadget: Rename usb_gadget_probe_driver() 2022-04-26 14:00:13 +02:00
config.c usb: fix various gadget panics on 10gbps cabling 2021-06-09 10:40:08 +02:00
configfs.c usb: gadget: configfs: Restrict symlink creation is UDC already binded 2023-03-10 09:33:35 +01:00
configfs.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
epautoconf.c usb: gadget: fix for a typo that conveys logically-inverted information. 2021-09-14 10:27:54 +02:00
functions.c USB: add SPDX identifiers to all remaining files in drivers/usb/ 2017-11-04 11:48:02 +01:00
Kconfig media: Kconfig: cleanup VIDEO_DEV dependencies 2022-03-18 05:58:35 +01:00
Makefile usb: gadget: Makefile: remove ccflags-y 2022-03-18 12:56:08 +01:00
u_f.c usb: gadget: Change Andrzej Pietrasiewicz's e-mail address 2019-02-11 11:12:29 +02:00
u_f.h USB: gadget: u_f: Unbreak offset calculation in VLAs 2020-08-27 09:25:06 +02:00
u_os_desc.h usb: gadget: Change Andrzej Pietrasiewicz's e-mail address 2019-02-11 11:12:29 +02:00
usbstring.c usb: gadget: fix langid kernel-doc warning in usbstring.c 2020-07-09 10:13:07 +03:00