In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: Fix possible deadlock in rfcomm_sk_state_change

syzbot reports a possible deadlock in rfcomm_sk_state_change [1].
While rfcomm_sock_connect acquires the sk lock and waits for
the rfcomm lock, rfcomm_sock_release could have the rfcomm
lock and hit a deadlock for acquiring the sk lock.
Here's a simplified flow:

rfcomm_sock_connect:
  lock_sock(sk)
  rfcomm_dlc_open:
    rfcomm_lock()

rfcomm_sock_release:
  rfcomm_sock_shutdown:
    rfcomm_lock()
    __rfcomm_dlc_close:
        rfcomm_k_state_change:
	  lock_sock(sk)

This patch drops the sk lock before calling rfcomm_dlc_open to
avoid the possible deadlock and holds sk's reference count to
prevent use-after-free after rfcomm_dlc_open completes.

https://git.kernel.org/stable/c/17511bd84871f4a6106cb335616e086880313f3f

https://git.kernel.org/stable/c/1d80d57ffcb55488f0ec0b77928d4f82d16b6a90

https://git.kernel.org/stable/c/98aec50ff7f60cc6f2d6a4396b475c547e58b04d