CVE-2022-49814

In the Linux kernel, the following vulnerability has been resolved: kcm: close race conditions on sk_receive_queue sk->sk_receive_queue is protected by skb queue lock, but for KCM sockets its RX path takes mux->rx_lock to protect more than just skb queue. However, kcm_recvmsg() still only grabs the skb queue lock, so race conditions still exist. We can teach kcm_recvmsg() to grab mux->rx_lock too but this would introduce a potential performance regression as struct kcm_mux can be shared by multiple KCM sockets. So we have to enforce skb queue lock in requeue_rx_msgs() and handle skb peek case carefully in kcm_wait_data(). Fortunately, skb_recv_datagram() already handles it nicely and is widely used by other sockets, we can just switch to skb_recv_datagram() after getting rid of the unnecessary sock lock in kcm_recvmsg() and kcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets, so it is safe to get rid of this check too. I ran the original syzbot reproducer for 30 min without seeing any issue.

• linux linux kernel (>= 4.6 < 4.14.300) • linux linux kernel (>= 4.15 < 4.19.267) • linux linux kernel (>= 4.20 < 5.4.225) • linux linux kernel (>= 5.5 < 5.10.156) • linux linux kernel (>= 5.11 < 5.15.80) • linux linux kernel (>= 5.16 < 6.0.10) • linux linux kernel 6.1