linux-kernel - Re: [PATCH v2 1/6] leds: netdev trigger: use memcpy in device_name

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Message-ID: <20190318112027.GA6101@amd>
Date:   Mon, 18 Mar 2019 12:20:28 +0100
From:   Pavel Machek <pavel@....cz>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-leds@...r.kernel.org
Subject: Re: [PATCH v2 1/6] leds: netdev trigger: use memcpy in
 device_name_store

On Thu 2019-03-14 15:06:14, Rasmus Villemoes wrote:
> If userspace doesn't end the input with a newline (which can easily
> happen if the write happens from a C program that does write(fd,
> iface, strlen(iface))), we may end up including garbage from a
> previous, longer value in the device_name. For example
> 
> # cat device_name
> 
> # printf 'eth12' > device_name
> # cat device_name
> eth12
> # printf 'eth3' > device_name
> # cat device_name
> eth32
> 
> I highly doubt anybody is relying on this behaviour, so switch to
> simply copying the bytes (we've already checked that size is <
> IFNAMSIZ) and unconditionally zero-terminate it; of course, we also
> still have to strip a trailing newline.
> 
> This is also preparation for future patches.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>

Acked-by: Pavel Machek <pavel@....cz>

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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