linux-kernel - Re: [PATCH v3 01/11] driver: platform: Add helper for safer setting of driver

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Message-ID: <20220228200326.GA516164@bhelgaas>
Date:   Mon, 28 Feb 2022 14:03:26 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Abel Vesa <abel.vesa@....com>, Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Andy Gross <agross@...nel.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, NXP Linux Team <linux-imx@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-hyperv@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-remoteproc@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, linux-spi@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH v3 01/11] driver: platform: Add helper for safer setting
 of driver_override

On Sun, Feb 27, 2022 at 02:52:04PM +0100, Krzysztof Kozlowski wrote:
> Several core drivers and buses expect that driver_override is a
> dynamically allocated memory thus later they can kfree() it.

> +int driver_set_override(struct device *dev, const char **override,
> +			const char *s, size_t len)
> +{
> +	const char *new, *old;
> +	char *cp;
> +
> +	if (!dev || !override || !s)
> +		return -EINVAL;
> +
> +	/* We need to keep extra room for a newline */

It would help a lot to extend this comment with a hint about where the
room for a newline is needed.  It was confusing even before, but it's
much more so now that the check is in a completely different file than
the "show" functions that need the space.

> +	if (len >= (PAGE_SIZE - 1))
> +		return -EINVAL;