swsusp: fix sysfs interface

The sysfs files /sys/power/disk and /sys/power/state do not work as
documented, since they allow the user to write only a few initial
characters of the input string to trigger the option (eg. 'echo pl >
/sys/power/disk' activates the platform mode of hibernation). Fix it.

Special thanks to Peter Moulder <[e-mail]> for
pointing out the problem.

Signed-off-by: Rafael J. Wysocki <[e-mail]>
Acked-by: Pavel Machek <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

kernel/power/disk.c

···
 
 	mutex_lock(&pm_mutex);
 	for (i = HIBERNATION_FIRST; i <= HIBERNATION_MAX; i++) {
-		if (!strncmp(buf, hibernation_modes[i], len)) {
+		if (len == strlen(hibernation_modes[i])
+		    && !strncmp(buf, hibernation_modes[i], len)) {
 			mode = i;
 			break;
 		}

kernel/power/main.c

···
 	len = p ? p - buf : n;
 
 	/* First, check if we are requested to hibernate */
-	if (!strncmp(buf, "disk", len)) {
+	if (len == 4 && !strncmp(buf, "disk", len)) {
 		error = hibernate();
 		return error ? error : n;
 	}
 
 	for (s = &pm_states[state]; state < PM_SUSPEND_MAX; s++, state++) {
-		if (*s && !strncmp(buf, *s, len))
+		if (*s && len == strlen(*s) && !strncmp(buf, *s, len))
 			break;
 	}
 	if (state < PM_SUSPEND_MAX && *s)