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 <[email protected]>

Cc Lars Ellenberg <[email protected]>

Cc "Christoph Böhmwalder" <[email protected]>

Cc Jens Axboe <[email protected]>

Cc [email protected]

Cc [email protected]

Signed-off-by Kees Cook <[email protected]>

---
  drivers/block/drbd/drbd_int.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

drivers/block/drbd/drbd_int.h +1 -1

index a30a5ed811be..7eecc53fae3d 100644
@@ -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);
 

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.

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