leds: trigger: netdev: use memcpy in device_name_store

Villemoes · jacek-anaszewski · commit 909346433064 · 2019-03-30T19:09:32.000+01:00
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: 06f502f ("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>
diff --git 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;
 

Original file line number	Diff line number	Diff line change
`@@ -122,7 +122,8 @@ static ssize_t device_name_store(struct device *dev,`
`122`	`122`	`trigger_data->net_dev = NULL;`
`123`	`123`	`}`
`124`	`124`
`125`		`- strncpy(trigger_data->device_name, buf, size);`
	`125`	`+ memcpy(trigger_data->device_name, buf, size);`
	`126`	`+ trigger_data->device_name[size] = 0;`
`126`	`127`	`if (size > 0 && trigger_data->device_name[size - 1] == '\n')`
`127`	`128`	`trigger_data->device_name[size - 1] = 0;`
`128`	`129`