netdev - Re: [PATCH] net: randomize layout of struct net

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Message-ID: <CAH4c4jJ_jKmPPOVfKKBbQzsQesNGdYbz4AWb9ZVZPpPEgtOP_g@mail.gmail.com>
Date: Mon, 2 Jun 2025 20:13:16 +0530
From: Pranav Tyagi <pranav.tyagi03@...il.com>
To: Kees Cook <kees@...nel.org>
Cc: andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, keescook@...omium.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	skhan@...uxfoundation.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH] net: randomize layout of struct net_device

On Mon, Jun 2, 2025 at 7:52 PM Pranav Tyagi <pranav.tyagi03@...il.com> wrote:
>
> On Mon, Jun 2, 2025 at 7:37 PM Kees Cook <kees@...nel.org> wrote:
> >
> >
> >
> > On June 2, 2025 6:59:32 AM PDT, Pranav Tyagi <pranav.tyagi03@...il.com> wrote:
> > >Add __randomize_layout to struct net_device to support structure layout
> > >randomization if CONFIG_RANDSTRUCT is enabled else the macro expands to
> > >do nothing. This enhances kernel protection by making it harder to
> > >predict the memory layout of this structure.
> > >
> > >Link: https://github.com/KSPP/linux/issues/188
> > >Signed-off-by: Pranav Tyagi <pranav.tyagi03@...il.com>
> > >---
> > > include/linux/netdevice.h | 4 ++++
> > > 1 file changed, 4 insertions(+)
> > >
> > >diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > >index 7ea022750e4e..0caff664ef3a 100644
> > >--- a/include/linux/netdevice.h
> > >+++ b/include/linux/netdevice.h
> > >@@ -2077,7 +2077,11 @@ enum netdev_reg_state {
> > >  *    moves out.
> > >  */
> > >
> > >+#ifdef CONFIG_RANDSTRUCT
> > >+struct __randomize_layout net_device {
> > >+#else
> > > struct net_device {
> > >+#endif
> >
> > There no need for the ifdef. Also these traditionally go at the end, between } and ;. See other examples in the tree.
> >
> > -Kees
>
> Thanks for the feedback. I will update the patch accordingly.

I also wanted to know if the __randomize_layout can go in between
struct and net_device as ____cacheline_aligned
is placed between } and ; at the end of the struct?
> >
> > >       /* Cacheline organization can be found documented in
> > >        * Documentation/networking/net_cachelines/net_device.rst.
> > >        * Please update the document when adding new fields.
> >
> > --
> > Kees Cook