[PATCH for-6.1 1/2] io_uring/net: fail zc send for unsupported protocols

[Pavel Begunkov <asml.silence@gmail.com>]

If a protocol doesn't support zerocopy it will silently fall back to
copying. This type of behaviour has always been a source of troubles
so it's better to fail such requests instead. For now explicitly
whitelist supported protocols in io_uring, which should be turned later
into a socket flag.

Cc: <stable@vger.kernel.org> # 6.0
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/net.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/io_uring/net.c b/io_uring/net.c
index 8c7226b5bf41..28127f1de1f0 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -120,6 +120,13 @@ static void io_netmsg_recycle(struct io_kiocb *req, unsigned int issue_flags)
 	}
 }
 
+static inline bool io_sock_support_zc(struct socket *sock)
+{
+	return likely(sock->sk && sk_fullsock(sock->sk) &&
+		     (sock->sk->sk_protocol == IPPROTO_TCP ||
+		      sock->sk->sk_protocol == IPPROTO_UDP));
+}
+
 static struct io_async_msghdr *io_msg_alloc_async(struct io_kiocb *req,
 						  unsigned int issue_flags)
 {
@@ -1056,6 +1063,8 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
 	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
 		return -ENOTSOCK;
+	if (!io_sock_support_zc(sock))
+		return -EOPNOTSUPP;
 
 	msg.msg_name = NULL;
 	msg.msg_control = NULL;
-- 
2.38.0