netdev - [PATCH net-next] udp: be less conservative with sock rmem accounting

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <d13b9808dad5f6e3fe3808bae3b4f64dfcee07fe.1480696423.git.pabeni@redhat.com>
Date:   Fri,  2 Dec 2016 17:35:49 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: [PATCH net-next] udp: be less conservative with sock rmem accounting

Before commit 850cbaddb52d ("udp: use it's own memory accounting
schema"), the udp protocol allowed sk_rmem_alloc to grow beyond
the rcvbuf by the whole current packet's truesize. After said commit
we allow sk_rmem_alloc to exceed the rcvbuf only if the receive queue
is empty. As reported by Jesper this cause a performance regression
for some (small) values of rcvbuf.

This commit is intended to fix the regression restoring the old
handling of the rcvbuf limit.

Reported-by: Jesper Dangaard Brouer <brouer@...hat.com>
Fixes: 850cbaddb52d ("udp: use it's own memory accounting schema")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/ipv4/udp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index e1d0bf8..16d88ba 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1205,14 +1205,14 @@ int __udp_enqueue_schedule_skb(struct sock *sk, struct sk_buff *skb)
 	 * queue is full; always allow at least a packet
 	 */
 	rmem = atomic_read(&sk->sk_rmem_alloc);
-	if (rmem && (rmem + size > sk->sk_rcvbuf))
+	if (rmem > sk->sk_rcvbuf)
 		goto drop;
 
 	/* we drop only if the receive buf is full and the receive
 	 * queue contains some other skb
 	 */
 	rmem = atomic_add_return(size, &sk->sk_rmem_alloc);
-	if ((rmem > sk->sk_rcvbuf) && (rmem > size))
+	if (rmem > (size + sk->sk_rcvbuf))
 		goto uncharge_drop;
 
 	spin_lock(&list->lock);
-- 
1.8.3.1