In the Linux kernel, the following vulnerability has been resolved: udp: Set SOCK_RCU_FREE earlier in udp_lib_get_port(). syzkaller triggered the warning [0] in udp_v4_early_demux(). In udp_v[46]_…

Summary

In the Linux kernel, the following vulnerability has been resolved: udp: Set SOCK_RCU_FREE earlier in udp_lib_get_port(). syzkaller triggered the warning [0] in udp_v4_early_demux(). In udp_v[46]_early_demux() and sk_lookup(), we do not touch the refcount of the looked-up sk and use sock_pfree() as skb->destructor, so we check SOCK_RCU_FREE to ensure that the sk is safe to access during the RCU grace period. Currently, SOCK_RCU_FREE is flagged for a bound socket after being put into the has…