Merge tag 'v6.11-rc6' into docs-mw

This is done primarily to get a docs build fix merged via another tree so
that "make htmldocs" stops failing.

1 files changed, 14 insertions, 0 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index fd17f25ff288..a4e510846905 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -97,6 +97,8 @@ static DEFINE_PER_CPU(struct sock_bh_locked, ipv4_tcp_sk) = {
 	.bh_lock = INIT_LOCAL_LOCK(bh_lock),
 };
 
+static DEFINE_MUTEX(tcp_exit_batch_mutex);
+
 static u32 tcp_v4_init_seq(const struct sk_buff *skb)
 {
 	return secure_tcp_seq(ip_hdr(skb)->daddr,
@@ -3514,6 +3516,16 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)
 {
 	struct net *net;
 
+	/* make sure concurrent calls to tcp_sk_exit_batch from net_cleanup_work
+	 * and failed setup_net error unwinding path are serialized.
+	 *
+	 * tcp_twsk_purge() handles twsk in any dead netns, not just those in
+	 * net_exit_list, the thread that dismantles a particular twsk must
+	 * do so without other thread progressing to refcount_dec_and_test() of
+	 * tcp_death_row.tw_refcount.
+	 */
+	mutex_lock(&tcp_exit_batch_mutex);
+
 	tcp_twsk_purge(net_exit_list);
 
 	list_for_each_entry(net, net_exit_list, exit_list) {
@@ -3521,6 +3533,8 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)
 		WARN_ON_ONCE(!refcount_dec_and_test(&net->ipv4.tcp_death_row.tw_refcount));
 		tcp_fastopen_ctx_destroy(net);
 	}
+
+	mutex_unlock(&tcp_exit_batch_mutex);
 }
 
 static struct pernet_operations __net_initdata tcp_sk_ops = {