From: Pavel Machek <pavel@ucw.cz>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Jacek Anaszewski" <jacek.anaszewski@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-leds@vger.kernel.org
Subject: Re: [PATCH 1/4] leds: netdev trigger: use memcpy in device_name_store
Date: Thu, 14 Mar 2019 11:14:19 +0100 [thread overview]
Message-ID: <20190314101419.GA14455@amd> (raw)
In-Reply-To: <20190313202615.22883-2-linux@rasmusvillemoes.dk>
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Hi!
> 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.
char device_name[IFNAMSIZ];
Ok, good catch reporting the bug, but are you sure the fix is right?
AFAICT the design is that device_name does _not_ have to be zero
terminated, and your fix incorrectly limits the size of device_name.
Pavel
> index 3dd3ed46d473..ddc2b90ad7ec 100644
> --- a/drivers/leds/trigger/ledtrig-netdev.c
> +++ b/drivers/leds/trigger/ledtrig-netdev.c
> @@ -122,7 +122,8 @@ static ssize_t device_name_store(struct device *dev,
> trigger_data->net_dev = NULL;
> }
>
> - strncpy(trigger_data->device_name, buf, size);
> + memcpy(trigger_data->device_name, buf, size);
> + trigger_data->device_name[size] = '\0';
I'd do = 0 for consistency with code below.
I believe the strncpy() is right to use here, but code should be
modified so that zero-termination is not required.
> if (size > 0 && trigger_data->device_name[size - 1] == '\n')
> trigger_data->device_name[size - 1] = 0;
>
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2019-03-14 10:14 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-11 10:59 replacement for CAN_LEDS Rasmus Villemoes
2019-03-11 14:42 ` Pavel Machek
2019-03-13 20:26 ` [PATCH 0/4] leds: netdev trigger: allow setting initial values in device tree Rasmus Villemoes
2019-03-13 20:26 ` [PATCH 1/4] leds: netdev trigger: use memcpy in device_name_store Rasmus Villemoes
2019-03-14 9:29 ` Uwe Kleine-König
2019-03-14 9:57 ` Rasmus Villemoes
2019-03-14 10:04 ` Uwe Kleine-König
2019-03-14 10:14 ` Pavel Machek [this message]
2019-03-14 10:54 ` Rasmus Villemoes
2019-03-14 12:16 ` Pavel Machek
2019-03-13 20:26 ` [PATCH 2/4] leds: netdev trigger: factor out middle part of device_name_store Rasmus Villemoes
2019-03-14 9:31 ` Uwe Kleine-König
2019-03-14 9:57 ` Rasmus Villemoes
2019-03-14 10:15 ` Pavel Machek
2019-03-14 10:20 ` Uwe Kleine-König
2019-03-13 20:26 ` [PATCH 3/4] leds: netdev trigger: add documentation to leds/common.txt Rasmus Villemoes
2019-03-13 20:26 ` [PATCH 4/4] leds: netdev trigger: allow setting initial values in device tree Rasmus Villemoes
2019-03-14 9:36 ` Uwe Kleine-König
2019-03-14 10:28 ` Rasmus Villemoes
2019-03-14 10:29 ` Pavel Machek
2019-03-14 11:26 ` Rasmus Villemoes
2019-03-14 12:00 ` Pavel Machek
2019-03-14 13:19 ` Rasmus Villemoes
2019-03-17 19:11 ` Pavel Machek
2019-03-24 20:39 ` Rasmus Villemoes
2019-03-14 10:32 ` Jacek Anaszewski
2019-03-14 14:06 ` [PATCH v2 0/6] " Rasmus Villemoes
2019-03-14 14:06 ` [PATCH v2 1/6] leds: netdev trigger: use memcpy in device_name_store Rasmus Villemoes
2019-03-18 11:20 ` Pavel Machek
2019-03-26 19:53 ` Jacek Anaszewski
2019-03-27 15:26 ` Rasmus Villemoes
2019-03-27 21:20 ` Jacek Anaszewski
2019-03-27 21:31 ` Rasmus Villemoes
2019-03-27 21:45 ` Jacek Anaszewski
2019-03-14 14:06 ` [PATCH v2 2/6] leds: netdev trigger: factor out middle part of device_name_store Rasmus Villemoes
2019-03-18 11:24 ` Pavel Machek
2019-03-14 14:06 ` [PATCH v2 3/6] leds: netdev trigger: move newline handling back to device_name_store Rasmus Villemoes
2019-03-18 11:25 ` Pavel Machek
2019-03-14 14:06 ` [PATCH v2 4/6] leds: netdev trigger: move name length checking to netdev_trig_set_device Rasmus Villemoes
2019-03-18 11:26 ` Pavel Machek
2019-03-14 14:06 ` [PATCH v2 5/6] leds: netdev trigger: add documentation to leds/common.txt Rasmus Villemoes
2019-03-14 14:06 ` [PATCH v2 6/6] leds: netdev trigger: allow setting initial values in device tree Rasmus Villemoes
2019-03-14 14:24 ` Jacek Anaszewski
2019-03-14 15:05 ` Rasmus Villemoes
2019-03-14 15:36 ` Jacek Anaszewski
2019-03-18 11:54 ` Pavel Machek
2019-03-28 16:28 ` Rob Herring
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