From: HanQuan Date: Tue, 23 Jun 2026 01:52:08 +0000 (+0000) Subject: net/tcp-ao: fix use-after-free of key in del_async path X-Git-Tag: v7.2-rc1~29^2~20 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5ba9950bc9078e19b69cca1e56d1553b125c6857;p=thirdparty%2Flinux.git net/tcp-ao: fix use-after-free of key in del_async path In tcp_ao_delete_key(), the del_async path skips the current_key and rnext_key validity checks present in the synchronous path, assuming these pointers are always NULL on LISTEN sockets. However, if a key was added with set_current=1/set_rnext=1 while the socket was in CLOSE state, current_key and rnext_key will be non-NULL after listen() transitions the socket to LISTEN. When such a key is deleted with del_async=1, hlist_del_rcu() and call_rcu() free the key without clearing the dangling pointers. After the RCU grace period, getsockopt(TCP_AO_INFO) dereferences current_key->sndid and rnext_key->rcvid from freed slab memory. Clear current_key and rnext_key in the del_async path when they reference the key being deleted. Fixes: d6732b95b6fb ("net/tcp: Allow asynchronous delete for TCP-AO keys (MKTs)") Signed-off-by: HanQuan Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260623015208.1191687-1-eilaimemedsnaimel@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c index 2f69bcecae78a..a56bb79e15e0e 100644 --- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -1747,6 +1747,10 @@ static int tcp_ao_delete_key(struct sock *sk, struct tcp_ao_info *ao_info, * them and we can just free all resources in RCU fashion. */ if (del_async) { + if (ao_info->current_key == key) + WRITE_ONCE(ao_info->current_key, NULL); + if (ao_info->rnext_key == key) + WRITE_ONCE(ao_info->rnext_key, NULL); atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc); call_rcu(&key->rcu, tcp_ao_key_free_rcu); return 0;