Re: [PATCH][next] hostap: Add __counted_by for struct prism2_download_data and use struct_size()

[Gustavo A. R. Silva]

On 10/9/23 21:54, Kees Cook wrote:
> 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/
>
> ?

Oops... sorry, I forgot I had reviewed this patch of yours.

> Yours is more complete since it includes the struct_size() change...

Should I resend this explicitly marking it as a v2?

--
Gustavo