io_uring: allow specific fd for IORING_OP_ACCEPT

sqe->len can be set to a specific fd we want to use for accept4(), so
it uses that one instead of just assigning a free unused one.

Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 14e779f1a292b95e25100ca5a875e72ecfab754b..5c9b97c06fdf8685ac9db3f9ec005054b8658216 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -354,6 +354,7 @@ struct io_accept {
        struct sockaddr __user          *addr;
        int __user                      *addr_len;
        int                             flags;
+       int                             open_fd;
 };
 
 struct io_sync {
@@ -3917,12 +3918,15 @@ static int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
        if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL|IORING_SETUP_SQPOLL)))
                return -EINVAL;
-       if (sqe->ioprio || sqe->len || sqe->buf_index)
+       if (sqe->ioprio || sqe->buf_index)
                return -EINVAL;
 
        accept->addr = u64_to_user_ptr(READ_ONCE(sqe->addr));
        accept->addr_len = u64_to_user_ptr(READ_ONCE(sqe->addr2));
        accept->flags = READ_ONCE(sqe->accept_flags);
+       accept->open_fd = READ_ONCE(sqe->len);
+       if (!(accept->flags & SOCK_SPECIFIC_FD) && accept->open_fd)
+               return -EINVAL;
        return 0;
 }
 
@@ -3934,7 +3938,8 @@ static int __io_accept(struct io_kiocb *req, bool force_nonblock)
 
        file_flags = force_nonblock ? O_NONBLOCK : 0;
        ret = __sys_accept4_file(req->file, file_flags, accept->addr,
-                                       accept->addr_len, accept->flags, -1);
+                                       accept->addr_len, accept->flags,
+                                       accept->open_fd);
        if (ret == -EAGAIN && force_nonblock)
                return -EAGAIN;
        if (ret == -ERESTARTSYS)