On Mon, Oct 09, 2023 at 01:41:18PM -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 <gustavoars@xxxxxxxxxx>
> ---
> drivers/net/wireless/intersil/hostap/hostap_download.c | 3 +--
> drivers/net/wireless/intersil/hostap/hostap_wlan.h | 2 +-
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/wireless/intersil/hostap/hostap_download.c b/drivers/net/wireless/intersil/hostap/hostap_download.c
> index 3672291ced5c..5e5bada28b5b 100644
> --- a/drivers/net/wireless/intersil/hostap/hostap_download.c
> +++ b/drivers/net/wireless/intersil/hostap/hostap_download.c
> @@ -732,8 +732,7 @@ static int prism2_download(local_info_t *local,
> goto out;
> }
>
> - dl = kzalloc(sizeof(*dl) + param->num_areas *
> - sizeof(struct prism2_download_data_area), GFP_KERNEL);
> + dl = kzalloc(struct_size(dl, data, param->num_areas), GFP_KERNEL);
> if (dl == NULL) {
> ret = -ENOMEM;
> goto out;
> diff --git a/drivers/net/wireless/intersil/hostap/hostap_wlan.h b/drivers/net/wireless/intersil/hostap/hostap_wlan.h
> index c25cd21d18bd..f71c0545c0be 100644
> --- a/drivers/net/wireless/intersil/hostap/hostap_wlan.h
> +++ b/drivers/net/wireless/intersil/hostap/hostap_wlan.h
> @@ -617,7 +617,7 @@ struct prism2_download_data {
> u32 addr; /* wlan card address */
> u32 len;
> u8 *data; /* allocated data */
> - } data[];
> + } data[] __counted_by(num_areas);
> };
Should this be considered a v2 of:
https://lore.kernel.org/linux-hardening/94848cc3-6f5c-46d7-8cc7-98a4f10865b3@xxxxxxxxxxxxxx/
?
Yours is more complete since it includes the struct_size() change...
--
Kees Cook
