4.18-stable review patch. If anyone has any objections, please let me know.
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From: Vincent Whitchurch vincent.whitchurch@axis.com
[ Upstream commit 5cf4a8532c992bb22a9ecd5f6d93f873f4eaccc2 ]
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 vincent.whitchurch@axis.com Acked-by: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/skbuff.c | 3 --- net/ipv4/tcp.c | 2 +- 2 files changed, 1 insertion(+), 4 deletions(-)
--- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -939,9 +939,6 @@ struct ubuf_info *sock_zerocopy_alloc(st
WARN_ON_ONCE(!in_task());
- if (!sock_flag(sk, SOCK_ZEROCOPY)) - return NULL; - skb = sock_omalloc(sk, 0, GFP_KERNEL); if (!skb) return NULL; --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -1186,7 +1186,7 @@ int tcp_sendmsg_locked(struct sock *sk,
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;