On Thu, Jan 05, 2023 at 11:05:11AM -0800, Kees Cook wrote:

Zero-length arrays are deprecated[1]. Replace struct io_uring_buf_ring's "bufs" with a flexible array member. (How is the size of this array verified?) Detected with GCC 13, using -fstrict-flex-arrays=3:

In function 'io_ring_buffer_select', inlined from 'io_buffer_select' at io_uring/kbuf.c:183:10: io_uring/kbuf.c:141:23: warning: array subscript 255 is outside the bounds of an interior zero-length array 'struct io_uring_buf[0]' [-Wzero-length-bounds] 141 | buf = &br->bufs[head]; | ^~~~~~~~~~~~~~~ In file included from include/linux/io_uring.h:7, from io_uring/kbuf.c:10: include/uapi/linux/io_uring.h: In function 'io_buffer_select': include/uapi/linux/io_uring.h:628:41: note: while referencing 'bufs' 628 | struct io_uring_buf bufs[0]; | ^~~~

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-a...

Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers") Cc: Jens Axboe axboe@kernel.dk Cc: Pavel Begunkov asml.silence@gmail.com Cc: "Gustavo A. R. Silva" gustavoars@kernel.org Cc: stable@vger.kernel.org Cc: io-uring@vger.kernel.org Signed-off-by: Kees Cook keescook@chromium.org

Reviewed-by: Gustavo A. R. Silva gustavoars@kernel.org

Thanks! -- Gustavo

---

v2: use helper since these flex arrays are in a union. v1: https://lore.kernel.org/lkml/20230105033743.never.628-kees@kernel.org

---

include/uapi/linux/io_uring.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 2780bce62faf..434f62e0fb72 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -625,7 +625,7 @@ struct io_uring_buf_ring { __u16 resv3; __u16 tail; };

• struct io_uring_buf	bufs[0];
  

• __DECLARE_FLEX_ARRAY(struct io_uring_buf, bufs);
  

  };

}; -- 2.34.1