net/tls: fix kernel panic when alloc_page failed

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

net/tls: fix kernel panic when alloc_page failed

We cannot set frag_list to NULL pointer when alloc_page failed.

It will be used in tls_strp_check_queue_ok when the next time

tls_strp_read_sock is called.

This is because we don't reset full_len in tls_strp_flush_anchor_copy()

so the recv path will try to continue handling the partial record

on the next call but we dettached the rcvq from the frag list.

Alternative fix would be to reset full_len.

Unable to handle kernel NULL pointer dereference

at virtual address 0000000000000028

Call trace:

tls_strp_check_rcv+0x128/0x27c

tls_strp_data_ready+0x34/0x44

tls_data_ready+0x3c/0x1f0

tcp_data_ready+0x9c/0xe4

tcp_data_queue+0xf6c/0x12d0

tcp_rcv_established+0x52c/0x798