linux-kernel - Re: [PATCH] net: randomize layout of struct net

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Message-ID: <EEF63CCD-BEED-4471-BF07-586452F4E0BE@kernel.org>
Date: Mon, 02 Jun 2025 07:07:23 -0700
From: Kees Cook <kees@...nel.org>
To: Pranav Tyagi <pranav.tyagi03@...il.com>, 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 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

> 	/* Cacheline organization can be found documented in
> 	 * Documentation/networking/net_cachelines/net_device.rst.
> 	 * Please update the document when adding new fields.

-- 
Kees Cook