RE: [Intel-wired-lan] [PATCH net-next 2/3] virtchnl: fix fake 1-elem arrays in structures allocated as `nents + 1`

[Romanowski, Rafal]

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@xxxxxxxxxx> On Behalf Of
> Kees Cook
> Sent: piątek, 4 sierpnia 2023 10:29
> To: Lobakin, Aleksander <aleksander.lobakin@xxxxxxxxx>
> Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>; Zaremba,
> Larysa <larysa.zaremba@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; Gustavo A. R.
> Silva <gustavoars@xxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Eric Dumazet
> <edumazet@xxxxxxxxxx>; intel-wired-lan@xxxxxxxxxxxxxxxx; linux-
> hardening@xxxxxxxxxxxxxxx; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo Abeni
> <pabeni@xxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>
> Subject: Re: [Intel-wired-lan] [PATCH net-next 2/3] virtchnl: fix fake 1-elem
> arrays in structures allocated as `nents + 1`
> 
> On Fri, Jul 28, 2023 at 05:52:06PM +0200, Alexander Lobakin wrote:
> > There are five virtchnl structures, which are allocated and checked in
> > the code as `nents + 1`, meaning that they always have memory for one
> > excessive element regardless of their actual number. This comes from
> > that their sizeof() includes space for 1 element and then they get
> > allocated via struct_size() or its open-coded equivalents, passing the
> > actual number of elements.
> > Expand virtchnl_struct_size() to handle such structures and replace
> > those 1-elem arrays with proper flex ones. Also fix several places
> > which open-code %IAVF_VIRTCHNL_VF_RESOURCE_SIZE. Finally, let the
> > virtchnl_ether_addr_list size be computed automatically when there's
> > no enough space for the whole list, otherwise we have to open-code
> > reverse struct_size() logics.
> >
> > Signed-off-by: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
> 
> I remain a fan of _Generic uses. :)
> 
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> 
> --
> Kees Cook
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Tested-by: Rafal Romanowski <rafal.romanowski@xxxxxxxxx>