drbd: Annotate struct fifo_buffer with __counted_by

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@linbit.com>
Cc: Lars Ellenberg <lars.ellenberg@linbit.com>
Cc: Christoph Böhmwalder <christoph.boehmwalder@linbit.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: drbd-dev@lists.linbit.com
Cc: linux-block@vger.kernel.org
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230915200316.never.707-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index a30a5ed811bea8e9f4486d004a9159f9a2a3cb9c..7eecc53fae3d39d32b4cbaea4f1cd6fcd5d75bae 100644 (file)
--- 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);