From 9da204cd67c4fe97e8aa465d10d5c2e7076f7f42 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 16 Dec 2022 16:29:17 +0000 Subject: [PATCH] net: stream: purge sk_error_queue in sk_stream_kill_queues() [ Upstream commit e0c8bccd40fc1c19e1d246c39bcf79e357e1ada3 ] Changheon Lee reported TCP socket leaks, with a nice repro. It seems we leak TCP sockets with the following sequence: 1) SOF_TIMESTAMPING_TX_ACK is enabled on the socket. Each ACK will cook an skb put in error queue, from __skb_tstamp_tx(). __skb_tstamp_tx() is using skb_clone(), unless SOF_TIMESTAMPING_OPT_TSONLY was also requested. 2) If the application is also using MSG_ZEROCOPY, then we put in the error queue cloned skbs that had a struct ubuf_info attached to them. Whenever an struct ubuf_info is allocated, sock_zerocopy_alloc() does a sock_hold(). As long as the cloned skbs are still in sk_error_queue, socket refcount is kept elevated. 3) Application closes the socket, while error queue is not empty. Since tcp_close() no longer purges the socket error queue, we might end up with a TCP socket with at least one skb in error queue keeping the socket alive forever. This bug can be (ab)used to consume all kernel memory and freeze the host. We need to purge the error queue, with proper synchronization against concurrent writers. Fixes: 24bcbe1cc69f ("net: stream: don't purge sk_error_queue in sk_stream_kill_queues()") Reported-by: Changheon Lee Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/core/stream.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/core/stream.c b/net/core/stream.c index a61130504827a..d7c5413d16d57 100644 --- a/net/core/stream.c +++ b/net/core/stream.c @@ -196,6 +196,12 @@ void sk_stream_kill_queues(struct sock *sk) /* First the read buffer. */ __skb_queue_purge(&sk->sk_receive_queue); + /* Next, the error queue. + * We need to use queue lock, because other threads might + * add packets to the queue without socket lock being held. + */ + skb_queue_purge(&sk->sk_error_queue); + /* Next, the write queue. */ WARN_ON(!skb_queue_empty(&sk->sk_write_queue));