From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rasmus Villemoes Subject: [PATCH 1/4] leds: netdev trigger: use memcpy in device_name_store Date: Wed, 13 Mar 2019 21:26:12 +0100 Message-ID: <20190313202615.22883-2-linux@rasmusvillemoes.dk> References: <20190311144227.GA4404@amd> <20190313202615.22883-1-linux@rasmusvillemoes.dk> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20190313202615.22883-1-linux@rasmusvillemoes.dk> Sender: linux-kernel-owner@vger.kernel.org To: Pavel Machek , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Jacek Anaszewski Cc: LKML , Rasmus Villemoes , linux-leds@vger.kernel.org List-Id: linux-leds@vger.kernel.org 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 --- drivers/leds/trigger/ledtrig-netdev.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c 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'; if (size > 0 && trigger_data->device_name[size - 1] == '\n') trigger_data->device_name[size - 1] = 0; -- 2.20.1