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leds: trigger: netdev: use memcpy in device_name_store

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[ Upstream commit 909346433064b8d840dc82af26161926b8d37558 ]

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.

Fixes: 06f502f57d ("leds: trigger: Introduce a NETDEV trigger")
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
This commit is contained in:
Rasmus Villemoes 2019-03-14 15:06:14 +01:00 committed by Greg Kroah-Hartman
parent 2663959af2
commit ee096f0dc4
1 changed files with 2 additions and 1 deletions
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3
drivers/leds/trigger/ledtrig-netdev.c
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@ -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;
if (size > 0 && trigger_data->device_name[size - 1] == '\n')
trigger_data->device_name[size - 1] = 0;