In the Linux kernel, the following vulnerability has been resolved: gtp: add synchronize_net() in gtp_newlink() error path to prevent use-a

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

gtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free

gtp_newlink()'s error path frees tid_hash and addr_hash without
waiting for an RCU grace period after clearing sk_user_data. A
concurrent gtp_encap_recv() in softirq may still hold the gtp_dev
pointer obtained via rcu_dereference_sk_user_data() and access the
freed memory.

BUG: KASAN: slab-use-after-free in gtp0_pdp_find+0x1f6/0x200 (gtp.c:152)
Call Trace:
<IRQ>
gtp0_pdp_find+0x1f6/0x200
gtp_encap_recv+0x527/0x24b0
udp_queue_rcv_one_skb+0x75f/0xc10

Add synchronize_net() before the kfree calls in out_hashtable, which
covers all error paths from both gtp_encap_enable() and
gtp_create_sockets().