linux-hardening - Re: [PATCH v4 7/8] net-device: Use new helpers from overflow.h in netdevice APIs

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Date: Thu, 29 Feb 2024 11:37:06 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Vinod Koul
 <vkoul@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, Jonathan
 Cameron <Jonathan.Cameron@...wei.com>, Mark Brown <broonie@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
 linux-spi@...r.kernel.org, netdev@...r.kernel.org,
 linux-hardening@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
 Lars-Peter Clausen <lars@...afoo.de>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: Re: [PATCH v4 7/8] net-device: Use new helpers from overflow.h in
 netdevice APIs

On Thu, 29 Feb 2024 11:08:58 -0800 Kees Cook wrote:
> > And some seem to be cargo-culted from out-of-tree code and are unused :S  
> 
> Ah, which can I remove?

The one in igc.h does not seem to be referenced by anything in the igc
directory. Pretty sure it's unused.

> As a further aside, this code:
> 
>         struct net_device *dev;
> 	...
>         struct net_device *p;
> 	...
>         /* ensure 32-byte alignment of whole construct */
>         alloc_size += NETDEV_ALIGN - 1;
>         p = kvzalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
> 	...
>         dev = PTR_ALIGN(p, NETDEV_ALIGN);
> 
> Really screams for a dynamic-sized (bucketed) kmem_cache_alloc
> API. Alignment constraints can be described in a regular kmem_cache
> allocator (rather than this open-coded version). I've been intending to
> build that for struct msg_msg for a while now, and here's another user. :)

TBH I'm not sure why we align it :S
NETDEV_ALIGN is 32B so maybe some old cache aligning thing?