[6.2,0754/1001] io_uring: Replace 0-length array with flexible array

Commit Message

Greg KH March 7, 2023, 4:58 p.m. UTC

From: Kees Cook <[e-mail]>

commit 36632d062975a9ff4410c90dd6d37922b68d0920 upstream.

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-and-one-element-arrays

Fixes: c7fb19428d67 ("io_uring: add support for ring mapped supplied buffers")
Cc: Jens Axboe <[e-mail]>
Cc: Pavel Begunkov <[e-mail]>
Cc: "Gustavo A. R. Silva" <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Kees Cook <[e-mail]>
Reviewed-by: Gustavo A. R. Silva <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>
---
 include/uapi/linux/io_uring.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

--- 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);
 	};
 };