io_uring/msg_ring: let target know allocated index

commit 5da28edd7bd5518f97175ecea77615bb729a7a28 upstream.

msg_ring requests transferring files support auto index selection via
IORING_FILE_INDEX_ALLOC, however they don't return the selected index
to the target ring and there is no other good way for the userspace to
know where is the receieved file.

Return the index for allocated slots and 0 otherwise, which is
consistent with other fixed file installing requests.

Cc: stable@vger.kernel.org # v6.0+
Fixes: e6130eba8a848 ("io_uring: add support for passing fixed file descriptors")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://github.com/axboe/liburing/issues/809
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
index 15602a136821b510a8201f90daf541b0c9188e08..be2695eb45ec164269b69120eda7319ec845d837 100644 (file)
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -183,7 +183,7 @@ static int io_msg_install_complete(struct io_kiocb *req, unsigned int issue_flag
         * completes with -EOVERFLOW, then the sender must ensure that a
         * later IORING_OP_MSG_RING delivers the message.
         */
-       if (!io_post_aux_cqe(target_ctx, msg->user_data, msg->len, 0))
+       if (!io_post_aux_cqe(target_ctx, msg->user_data, ret, 0))
                ret = -EOVERFLOW;
 out_unlock:
        io_double_unlock_ctx(target_ctx);
@@ -210,6 +210,8 @@ static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
        struct io_ring_ctx *ctx = req->ctx;
        struct file *src_file = msg->src_file;
 
+       if (msg->len)
+               return -EINVAL;
        if (target_ctx == ctx)
                return -EINVAL;
        if (target_ctx->flags & IORING_SETUP_R_DISABLED)