Re: [PATCH 7/8] mtd: rawnand: qcom: Early structure initialization

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: Manivannan Sadhasivam <mani@kernel.org>,
	Md Sadre Alam <quic_mdalam@quicinc.com>,
	Sricharan Ramabadhran <quic_srichara@quicinc.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Pratyush Yadav <pratyush@kernel.org>,
	Michael Walle <michael@walle.cc>,
	linux-mtd@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 7/8] mtd: rawnand: qcom: Early structure initialization
Date: Thu, 27 Jul 2023 17:14:11 +0200	[thread overview]
Message-ID: <20230727171411.0efd4815@xps-13> (raw)
In-Reply-To: <d83011fa-79e8-0ce8-4fdc-de01c43775f9@linaro.org>

Hi Tudor,

tudor.ambarus@linaro.org wrote on Thu, 27 Jul 2023 16:03:40 +0100:

> On 7/16/23 15:46, Miquel Raynal wrote:
> > Instead of allocating a structure on the stack with random data and then
> > expect the callee to perform the initialization (which is, in general,
> > error prone), prefer zeroing the structure explicitly at allocation and
> > provide the already zeroed area, so no explicit memset operation is
> > needed. It is probably safer to do so, so we limit the timeframe when
> > dirty data could actually be accessed by mistake.  
> 
> Why is zeroed data considered safe or sane?

I believe allocating structures like that on the stack will make their
content inherit from previous values used there, which is generally a
bad idea if we expect the structure to be zeroed, which is the case
here.

This structure is meant to be zeroed before being used, so instead of
carrying stale data that will be wiped off later, I prefer to have it
zeroed earlier. Reducing the time when one could access stale data or
write something that will be reset does not sound totally useless to
me, in particular given the number of changes this driver has been
subject to recently.

Thanks,
Miquèl

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