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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 f214f915e7 ("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: f214f915e7 ("tcp: enable MSG_ZEROCOPY")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vincent Whitchurch 2018-09-06 15:54:59 +02:00 committed by David S. Miller
parent a162c35114
commit 5cf4a8532c
2 changed files with 1 additions and 4 deletions
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3
net/core/skbuff.c
View File

@ -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;

2
net/ipv4/tcp.c
View File

@ -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;