io_uring/net: fail zc send when unsupported by socket

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.

Cc: <stable@vger.kernel.org> # 6.0
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2db3c7f16bb6efab4b04569cd16e6242b40c5cb3.1666346426.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/net.c b/io_uring/net.c
index 8c7226b..26ff367 100644 (file)
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1056,6 +1056,8 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
        sock = sock_from_file(req->file);
        if (unlikely(!sock))
                return -ENOTSOCK;
+       if (!test_bit(SOCK_SUPPORT_ZC, &sock->flags))
+               return -EOPNOTSUPP;
 
        msg.msg_name = NULL;
        msg.msg_control = NULL;