From 5cf4a8532c992bb22a9ecd5f6d93f873f4eaccc2 Mon Sep 17 00:00:00 2001 From: Vincent Whitchurch Date: Thu, 6 Sep 2018 15:54:59 +0200 Subject: [PATCH] tcp: really ignore MSG_ZEROCOPY if no SO_ZEROCOPY According to the documentation in msg_zerocopy.rst, the SO_ZEROCOPY flag was introduced because send(2) ignores unknown message flags and any legacy application which was accidentally passing the equivalent of MSG_ZEROCOPY earlier should not see any new behaviour. Before commit f214f915e7db ("tcp: enable MSG_ZEROCOPY"), a send(2) call which passed the equivalent of MSG_ZEROCOPY without setting SO_ZEROCOPY would succeed. However, after that commit, it fails with -ENOBUFS. So it appears that the SO_ZEROCOPY flag fails to fulfill its intended purpose. Fix it. Fixes: f214f915e7db ("tcp: enable MSG_ZEROCOPY") Signed-off-by: Vincent Whitchurch Acked-by: Willem de Bruijn Signed-off-by: David S. Miller --- net/core/skbuff.c | 3 --- net/ipv4/tcp.c | 2 +- 2 files changed, 1 insertion(+), 4 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index c996c09..b2c807f 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -939,9 +939,6 @@ struct ubuf_info *sock_zerocopy_alloc(struct sock *sk, size_t size) WARN_ON_ONCE(!in_task()); - if (!sock_flag(sk, SOCK_ZEROCOPY)) - return NULL; - skb = sock_omalloc(sk, 0, GFP_KERNEL); if (!skb) return NULL; diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index b8af2fe..10c6246 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1185,7 +1185,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size) flags = msg->msg_flags; - if (flags & MSG_ZEROCOPY && size) { + if (flags & MSG_ZEROCOPY && size && sock_flag(sk, SOCK_ZEROCOPY)) { if (sk->sk_state != TCP_ESTABLISHED) { err = -EINVAL; goto out_err; -- 2.7.4