io_uring/net: improve zc addr import error handling

We may account memory to a memcg of a request that didn't even got to
the network layer. It's not a bug as it'll be routinely cleaned up on
flush, but it might be confusing for the userspace.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b8aae61f4c3ddc4da97c1da876bb73871f352d50.1660566179.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/net.c

@@ -977,6 +977,14 @@ int io_sendzc(struct io_kiocb *req, unsigned int issue_flags)
 	msg.msg_controllen = 0;
 	msg.msg_namelen = 0;
 
+	if (zc->addr) {
+		ret = move_addr_to_kernel(zc->addr, zc->addr_len, &address);
+		if (unlikely(ret < 0))
+			return ret;
+		msg.msg_name = (struct sockaddr *)&address;
+		msg.msg_namelen = zc->addr_len;
+	}
+
 	if (zc->flags & IORING_RECVSEND_FIXED_BUF) {
 		ret = io_import_fixed(WRITE, &msg.msg_iter, req->imu,
 					(u64)(uintptr_t)zc->buf, zc->len);
@@ -992,14 +1000,6 @@ int io_sendzc(struct io_kiocb *req, unsigned int issue_flags)
 			return ret;
 	}
 
-	if (zc->addr) {
-		ret = move_addr_to_kernel(zc->addr, zc->addr_len, &address);
-		if (unlikely(ret < 0))
-			return ret;
-		msg.msg_name = (struct sockaddr *)&address;
-		msg.msg_namelen = zc->addr_len;
-	}
-
 	msg_flags = zc->msg_flags | MSG_ZEROCOPY;
 	if (issue_flags & IO_URING_F_NONBLOCK)
 		msg_flags |= MSG_DONTWAIT;