From: Eric Dumazet <edumazet@google.com>
Date: Thu, 8 Dec 2016 19:41:57 +0000 (-0800)
Subject: udp: udp_rmem_release() should touch sk_rmem_alloc later
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=02ab0d139cff1efc5aa1fb4378c727668334fe97;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

udp: udp_rmem_release() should touch sk_rmem_alloc later

In flood situations, keeping sk_rmem_alloc at a high value
prevents producers from touching the socket.

It makes sense to lower sk_rmem_alloc only at the end
of udp_rmem_release() after the thread draining receive
queue in udp_recvmsg() finished the writes to sk_forward_alloc.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 5a38faa12cde..9ca279b130d5 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1191,13 +1191,14 @@ static void udp_rmem_release(struct sock *sk, int size, int partial)
 	}
 	up->forward_deficit = 0;
 
-	atomic_sub(size, &sk->sk_rmem_alloc);
 	sk->sk_forward_alloc += size;
 	amt = (sk->sk_forward_alloc - partial) & ~(SK_MEM_QUANTUM - 1);
 	sk->sk_forward_alloc -= amt;
 
 	if (amt)
 		__sk_mem_reduce_allocated(sk, amt >> SK_MEM_QUANTUM_SHIFT);
+
+	atomic_sub(size, &sk->sk_rmem_alloc);
 }
 
 /* Note: called with sk_receive_queue.lock held.