usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait While performing fast composition switch, there is a possibility that the process of ffs_ep0_write/ffs_ep0_read get into a race condition due to ep0req being freed up from functionfs_unbind. Consider the scenario that the ffs_ep0_write calls the ffs_ep0_queue_wait by taking a lock &ffs->ev.waitq.lock. However, the functionfs_unbind isn't bounded so it can go ahead and mark the ep0req to NULL, and since there is no NULL check in ffs_ep0_queue_wait we will end up in use-after-free. Fix this by making a serialized execution between the two functions using a mutex_lock(ffs->mutex).

References

• https://git.kernel.org/stable/c/facf353c9e8d7885b686d9a4b173d4e0af6441d2
• https://git.kernel.org/stable/c/e9036e951f93fb8d7b5e9d6e2c7f94a4da312ae4
• https://git.kernel.org/stable/c/a8d40942df074f4ebcb9bd3413596d92f323b064
• https://git.kernel.org/stable/c/6dd9ea05534f323668db94fcc2726c7a84547e78
• https://git.kernel.org/stable/c/ae8e136bcaae96163b5821984de1036efc9abb1a
• https://git.kernel.org/stable/c/6aee197b7fbcd61596a78b47d553f2f99111f217
• https://git.kernel.org/stable/c/6a19da111057f69214b97c62fb0ac59023970850