io_uring: ignore ->buf_index if REQ_F_BUFFER_SELECT isn't set

There's no point in validity checking buf_index if the request doesn't
have REQ_F_BUFFER_SELECT set, as we will never use it for that case.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3573,10 +3573,6 @@ static struct iovec *__io_import_iovec(int rw, struct io_kiocb *req,
 		return NULL;
 	}
 
-	/* buffer index only valid with fixed read/write, or buffer select  */
-	if (unlikely(req->buf_index && !(req->flags & REQ_F_BUFFER_SELECT)))
-		return ERR_PTR(-EINVAL);
-
 	buf = u64_to_user_ptr(req->rw.addr);
 	sqe_len = req->rw.len;