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

From: Jakub Kicinski <kuba@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Vinod Koul <vkoul@kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	Mark Brown <broonie@kernel.org>,
	linux-arm-kernel@lists.infradead.org, dmaengine@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
	linux-spi@vger.kernel.org, netdev@vger.kernel.org,
	linux-hardening@vger.kernel.org,
	Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Paolo Abeni <pabeni@redhat.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>
Subject: Re: [PATCH v4 7/8] net-device: Use new helpers from overflow.h in netdevice APIs
Date: Thu, 29 Feb 2024 11:37:06 -0800	[thread overview]
Message-ID: <20240229113706.42c877a1@kernel.org> (raw)
In-Reply-To: <202402291059.491B5E03@keescook>

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?