On Mon, Oct 09, 2023 at 02:33:01PM -0600, Gustavo A. R. Silva wrote:
>
>
> 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?
I defer to Kalle -- your Subject is more accurate, so perhaps let's just
let this stand?
--
Kees Cook
