linux-hardening - Re: [PATCH net-next v4 5/8] mfd: zl3073x: Add functions to work with register mailboxes

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Message-ID: <8082254c-01a6-4aca-84de-76083fdcbb3b@lunn.ch>
Date: Thu, 24 Apr 2025 21:18:33 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Ivan Vecera <ivecera@...hat.com>
Cc: netdev@...r.kernel.org, Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
	Jiri Pirko <jiri@...nulli.us>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Prathosh Satish <Prathosh.Satish@...rochip.com>,
	Lee Jones <lee@...nel.org>, Kees Cook <kees@...nel.org>,
	Andy Shevchenko <andy@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Schmidt <mschmidt@...hat.com>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH net-next v4 5/8] mfd: zl3073x: Add functions to work with
 register mailboxes

> During taking 613cbb91e9ce ("media: Add MIPI CCI register access helper
> functions") approach I found they are using for these functions u64
> regardless of register size... Just to accommodate the biggest
> possible value. I know about weakness of 'void *' usage but u64 is not
> also ideal as the caller is forced to pass always 8 bytes for reading
> and forced to reserve 8 bytes for each read value on stack.

In this device, how are the u48s used? Are they actually u48s, or are
they just u8[6], for example a MAC address? The network stack has lots
of functions like:

eth_hw_addr_set(struct net_device *dev, const u8 *addr)

and it is assumed that *addr is ETH_ALEN bytes in length. There is no
direct typing checking for this by the compiler, but the compiler is
getting smarter at checking for buffer overruns over function calls.

	Andrew