Re: [PATCH] niu: Silence randstruct warnings

[Kees Cook]

On Wed, May 11, 2022 at 03:16:47PM -0700, Jakub Kicinski wrote:
> On Tue, 10 May 2022 13:57:29 -0700 Kees Cook wrote:
> > Clang randstruct gets upset when it sees struct addresspace (which is
> > randomized) being assigned to a struct page (which is not randomized):
> > 
> > drivers/net/ethernet/sun/niu.c:3385:12: error: casting from randomized structure pointer type 'struct address_space *' to 'struct page *'
> >                         *link = (struct page *) page->mapping;
> >                                 ^
> > 
> > It looks like niu.c is looking for an in-line place to chain its allocated
> > pages together and is overloading the "mapping" member, as it is unused.
> > This is very non-standard, and is expected to be cleaned up in the
> > future[1], but there is no "correct" way to handle it today.
> > 
> > No meaningful machine code changes result after this change, and source
> > readability is improved.
> > 
> > Drop the randstruct exception now that there is no "confusing" cross-type
> > assignment.
> > 
> > [1] https://lore.kernel.org/lkml/YnqgjVoMDu5v9PNG@xxxxxxxxxxxxxxxxxxxx/
> > 
> > Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> > Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> > Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> > Cc: Du Cheng <ducheng2@xxxxxxxxx>
> > Cc: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > Cc: Vlastimil Babka <vbabka@xxxxxxx>
> > Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
> > Cc: netdev@xxxxxxxxxxxxxxx
> > Cc: linux-mm@xxxxxxxxx
> > Cc: linux-hardening@xxxxxxxxxxxxxxx
> > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> 
> I presume you prefer to take this one via your tree too, so:

Yeah, that's easiest for the exception removals.

> Acked-by: Jakub Kicinski <kuba@xxxxxxxxxx>

Thanks!

-- 
Kees Cook