Re: [syzbot] [mptcp?] KASAN: slab-use-after-free Read in __timer_delete_sync

[Edward Adam Davis]

entry need to be protected by pm.lock.

#syz test

diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 3e4ad801786f..d28bf0c9ad66 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -336,11 +336,12 @@ mptcp_pm_del_add_timer(struct mptcp_sock *msk,
 	entry = mptcp_lookup_anno_list_by_saddr(msk, addr);
 	if (entry && (!check_id || entry->addr.id == addr->id))
 		entry->retrans_times = ADD_ADDR_RETRANS_MAX;
-	spin_unlock_bh(&msk->pm.lock);
 
 	if (entry && (!check_id || entry->addr.id == addr->id))
 		sk_stop_timer_sync(sk, &entry->add_timer);
 
+	spin_unlock_bh(&msk->pm.lock);
+
 	return entry;
 }