[PATCH] udf: Annotate struct udf_bitmap with __counted_by

[Kees Cook <keescook@chromium.org>]

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 udf_bitmap.

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

Cc: Jan Kara <jack@suse.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/udf/udf_sb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/udf_sb.h b/fs/udf/udf_sb.h
index 9af6ff7f9747..f9a60bc1abcf 100644
--- a/fs/udf/udf_sb.h
+++ b/fs/udf/udf_sb.h
@@ -86,7 +86,7 @@ struct udf_virtual_data {
 struct udf_bitmap {
 	__u32			s_extPosition;
 	int			s_nr_groups;
-	struct buffer_head	*s_block_bitmap[];
+	struct buffer_head	*s_block_bitmap[] __counted_by(s_nr_groups);
 };
 
 struct udf_part_map {
-- 
2.34.1