netdev - [PATCH net] net: let skb_orphan

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Date:   Tue, 30 Mar 2021 16:24:32 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] 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.

Address the issue invoking the write_space callback after
releasing the memory, if the old skb destructor requires that.

Fixes: f6ba8d33cfbb ("netem: fix skb_orphan_partial()")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/core/sock.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/sock.c b/net/core/sock.c
index 0ed98f20448a2..7a38332d748e7 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2137,6 +2137,8 @@ void skb_orphan_partial(struct sk_buff *skb)

 		if (refcount_inc_not_zero(&sk->sk_refcnt)) {
 			WARN_ON(refcount_sub_and_test(skb->truesize, &sk->sk_wmem_alloc));
+			if (skb->destructor == sock_wfree)
+				sk->sk_write_space(sk);
 			skb->destructor = sock_efree;
 		}
 	} else {
-- 
2.26.2