netdev - [PATCH net] Revert "udp: do rmem bulk free even if the rx sk queue is empty"

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Date:   Tue, 21 Jan 2020 16:50:49 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Subject: [PATCH net] Revert "udp: do rmem bulk free even if the rx sk queue is empty"

This reverts commit 0d4a6608f68c7532dcbfec2ea1150c9761767d03.

Williem reported that after commit 0d4a6608f68c ("udp: do rmem bulk
free even if the rx sk queue is empty") the memory allocated by
an almost idle system with many UDP sockets can grow a lot.

For stable kernel keep the solution as simple as possible and revert
the offending commit.

Reported-by: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Diagnosed-by: Eric Dumazet <eric.dumazet@...il.com>
Fixes: 0d4a6608f68c ("udp: do rmem bulk free even if the rx sk queue is empty")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/ipv4/udp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 93a355b6b092..030d43c7c957 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1368,7 +1368,8 @@ static void udp_rmem_release(struct sock *sk, int size, int partial,
 	if (likely(partial)) {
 		up->forward_deficit += size;
 		size = up->forward_deficit;
-		if (size < (sk->sk_rcvbuf >> 2))
+		if (size < (sk->sk_rcvbuf >> 2) &&
+		    !skb_queue_empty(&up->reader_queue))
 			return;
 	} else {
 		size += up->forward_deficit;
-- 
2.21.0