[PATCH] drbd: Annotate struct fifo_buffer with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct fifo_buffer.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Cc: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
Cc: "Christoph Böhmwalder" <christoph.boehmwalder@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: drbd-dev@xxxxxxxxxxxxxxxx
Cc: linux-block@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 drivers/block/drbd/drbd_int.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index a30a5ed811be..7eecc53fae3d 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -553,7 +553,7 @@ struct fifo_buffer {
 	unsigned int head_index;
 	unsigned int size;
 	int total; /* sum of all values */
-	int values[];
+	int values[] __counted_by(size);
 };
 extern struct fifo_buffer *fifo_alloc(unsigned int fifo_size);
 
-- 
2.34.1