tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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l2tp: avoid overriding sk->sk_user_data

Although commit 4a4cd70369f1 ("l2tp: don't set sk_user_data in tunnel socket")
removed sk->sk_user_data usage, setup_udp_tunnel_sock() still touches
sk->sk_user_data, this conflicts with sockmap which also leverages
sk->sk_user_data to save psock.

Restore this sk->sk_user_data check to avoid such conflicts.

Fixes: 4a4cd70369f1 ("l2tp: don't set sk_user_data in tunnel socket")
Reported-by: syzbot+8dbe3133b840c470da0e@syzkaller.appspotmail.com
Cc: Tom Parkin <tparkin@katalix.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Tested-by: James Chapman <jchapman@katalix.com>
Reviewed-by: James Chapman <jchapman@katalix.com>
Link: https://patch.msgid.link/20240822182544.378169-1-xiyou.wangcong@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

authored by

Cong Wang and committed by
Jakub Kicinski 1461f5a3 7888173e

+3
+3
net/l2tp/l2tp_core.c
··· 1620 1620 (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP)) 1621 1621 return -EPROTONOSUPPORT; 1622 1622 1623 + if (encap == L2TP_ENCAPTYPE_UDP && sk->sk_user_data) 1624 + return -EBUSY; 1625 + 1623 1626 tunnel = l2tp_sk_to_tunnel(sk); 1624 1627 if (tunnel) { 1625 1628 l2tp_tunnel_put(tunnel);