x86, mce: Fix set_trigger() accessor

Fix the condition checking the result of strchr() (which previously
could result in an oops), and make the function return the number of
bytes actively used.

[ Impact: fix oops ]

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <andi@firstfloor.org>
LKML-Reference: <4A5F04B7020000780000AB59@vpn.id2.novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/cpu/mcheck/mce.c

@@ -1692,17 +1692,15 @@ static ssize_t set_trigger(struct sys_device *s, struct sysdev_attribute *attr,
 				const char *buf, size_t siz)
 {
 	char *p;
-	int len;
 
 	strncpy(mce_helper, buf, sizeof(mce_helper));
 	mce_helper[sizeof(mce_helper)-1] = 0;
-	len = strlen(mce_helper);
 	p = strchr(mce_helper, '\n');
 
-	if (*p)
+	if (p)
 		*p = 0;
 
-	return len;
+	return strlen(mce_helper) + !!p;
 }
 
 static ssize_t set_ignore_ce(struct sys_device *s,