Commit 9adc89af authored Mar 30, 2021 by Paolo Abeni Committed by David S. Miller Mar 30, 2021

net: let skb_orphan_partial wake-up waiters.



Currently the mentioned helper can end-up freeing the socket wmem
without waking-up any processes waiting for more write memory.

If the partially orphaned skb is attached to an UDP (or raw) socket,
the lack of wake-up can hang the user-space.

Even for TCP sockets not calling the sk destructor could have bad
effects on TSQ.

Address the issue using skb_orphan to release the sk wmem before
setting the new sock_efree destructor. Additionally bundle the
whole ownership update in a new helper, so that later other
potential users could avoid duplicate code.

v1 -> v2:
 - use skb_orphan() instead of sort of open coding it (Eric)
 - provide an helper for the ownership change (Eric)

Fixes: f6ba8d33 ("netem: fix skb_orphan_partial()")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent ae81feb7

include/net/sock.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -2221,6 +2221,15 @@ static inline void skb_set_owner_r(struct sk_buff skb, struct sock sk)
		sk_mem_charge(sk, skb->truesize);
		}

		static inline void skb_set_owner_sk_safe(struct sk_buff skb, struct sock sk)
		{
		if (sk && refcount_inc_not_zero(&sk->sk_refcnt)) {
		skb_orphan(skb);
		skb->destructor = sock_efree;
		skb->sk = sk;
		}
		}

		void sk_reset_timer(struct sock sk, struct timer_list timer,
		unsigned long expires);

net/core/sock.c

+3 −9

Original line number	Diff line number	Diff line
		@@ -2132,17 +2132,11 @@ void skb_orphan_partial(struct sk_buff *skb)
		if (skb_is_tcp_pure_ack(skb))
		return;

		if (can_skb_orphan_partial(skb)) {
		struct sock *sk = skb->sk;

		if (refcount_inc_not_zero(&sk->sk_refcnt)) {
		WARN_ON(refcount_sub_and_test(skb->truesize, &sk->sk_wmem_alloc));
		skb->destructor = sock_efree;
		}
		} else {
		if (can_skb_orphan_partial(skb))
		skb_set_owner_sk_safe(skb, skb->sk);
		else
		skb_orphan(skb);
		}
		}
		EXPORT_SYMBOL(skb_orphan_partial);

		/*