In the Linux kernel, the following vulnerability has been resolved:
net/af_iucv: fix NULL deref in afiucv_hs_callback_syn()
afiucv_hs_callback_syn() allocates the child socket with GFP_ATOMIC. If the allocation fails, nsk is NULL.
The connection-refused path is entered when the listen state check fails, the accept backlog is full, or nsk is NULL. The code unconditionally calls iucv_sock_kill(nsk) in that path.
iucv_sock_kill() does not accept a NULL socket pointer and immediately dereferences sk via sock_flag(sk, SOCK_ZAPPED). When nsk is NULL, calling iucv_sock_kill(nsk) results in a NULL pointer dereference.
Only call iucv_sock_kill() when a child socket was successfully allocated.
References
- https://git.kernel.org/stable/c/0e857185591fe79934427c9c0c1c31dc776be134
- https://git.kernel.org/stable/c/33736ff5e7c97d3348ce812e8bd2e125d840743c
- https://git.kernel.org/stable/c/46453b16f38ec7147351f7447e2aec6ea330f7b3
- https://git.kernel.org/stable/c/47a5116e56a6b6fe1e909f244e39cd0fc26ceee4
- https://git.kernel.org/stable/c/8bb111f87ded6acb9837ec9b45d6f02cda94c51f