io_uring: allow 0 length for buffer select

If user gives 0 for length, we can set it from the available buffer size.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220630091231.1456789-2-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 5e00f16e89b866b0198ee24a6cf42c8471268b3f..e538fa7cb727cf486fdf9c00e7aa6b67e2c22d3d 100644 (file)
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -115,7 +115,7 @@ static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
 
                kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
                list_del(&kbuf->list);
-               if (*len > kbuf->len)
+               if (*len == 0 || *len > kbuf->len)
                        *len = kbuf->len;
                req->flags |= REQ_F_BUFFER_SELECTED;
                req->kbuf = kbuf;
@@ -145,7 +145,7 @@ static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
                buf = page_address(bl->buf_pages[index]);
                buf += off;
        }
-       if (*len > buf->len)
+       if (*len == 0 || *len > buf->len)
                *len = buf->len;
        req->flags |= REQ_F_BUFFER_RING;
        req->buf_list = bl;