On Tue, Oct 10, 2023 at 06:59:44AM -0600, Gustavo A. R. Silva wrote:
> 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 via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
>
> While there, use struct_size() helper, instead of the open-coded
> version, to calculate the size for the allocation of the whole
> flexible structure, including of course, the flexible-array member.
>
> This code was found with the help of Coccinelle, and audited and
> fixed manually.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org>
> ---
> fs/afs/internal.h | 2 +-
> fs/afs/xattr.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/afs/internal.h b/fs/afs/internal.h
> index 469a717467a4..e263a58b82ba 100644
> --- a/fs/afs/internal.h
> +++ b/fs/afs/internal.h
> @@ -1116,7 +1116,7 @@ extern void afs_fs_inline_bulk_status(struct
> afs_operation *);
>
> struct afs_acl {
> u32 size;
> - u8 data[];
> + u8 data[] __counted_by(size);
> };
It's surprising how many of these 2-member structs we have in the kernel
that do the same basic thing. :)
And I see that "size" is assigned before using "data", good.
Reviewed-by: Kees Cook <keesc...@chromium.org>
-Kees
--
Kees Cook
