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.