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

Bluetooth: L2CAP: Fix use-after-free in l2cap_sock_new_connection_cb()

l2cap_sock_new_connection_cb() returned l2cap_pi(sk)->chan after
release_sock(parent). Once the parent lock is dropped the newly
enqueued child socket sk is reachable via the accept queue, so another
task can accept and free it before the callback dereferences sk,
resulting in a use-after-free.

Rework the ->new_connection() op so the core, rather than the callback,
owns the child channel's lifetime. The op now receives a pre-allocated
new_chan and returns an errno instead of allocating and returning a
channel. l2cap_new_connection() allocates the child channel and links
it into the conn list via __l2cap_chan_add() before invoking the
callback, so the conn-list reference keeps the channel alive once
release_sock(parent) exposes the socket to other tasks.

Channel configuration that was duplicated in l2cap_sock_init() and the
various new_connection callbacks is consolidated into
l2cap_chan_set_defaults(), which now inherits from the parent channel
when one is supplied.

https://git.kernel.org/stable/c/36da806f7fbaee56ad9e81859deec203f9728700

https://git.kernel.org/stable/c/6fef032af0092ed5ccb767239a9ac1bc38c08a40

https://git.kernel.org/stable/c/733e76e74e406c1d1ddc7369420dd8a47f48bb8a

https://git.kernel.org/stable/c/84e718b6a814edc84159361f9f454a4e92ae91ae

https://git.kernel.org/stable/c/8c37e4338c801ebb8cee52436c01c41e009f6e87

https://git.kernel.org/stable/c/b39298044e5534612511a2ff5de03ba5f6e7a820

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