proc_dointvec: write a single value

The commit 00b7c3395aec3df43de5bd02a3c5a099ca51169f
"sysctl: refactor integer handling proc code"
modified the behaviour of writing to /proc.
Before the commit, write("1\n") to /proc/sys/kernel/printk succeeded. But
now it returns EINVAL.

This commit supports writing a single value to a multi-valued entry.

Signed-off-by: J. R. Okajima <[e-mail]>
Reviewed-and-tested-by: WANG Cong <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

kernel/sysctl.c

···
 		if (write) {
 			left -= proc_skip_spaces(&kbuf);
 
+			if (!left)
+				break;
 			err = proc_get_long(&kbuf, &left, &lval, &neg,
 					     proc_wspace_sep,
 					     sizeof(proc_wspace_sep), NULL);
···
 
 	if (!write && !first && left && !err)
 		err = proc_put_char(&buffer, &left, '\n');
-	if (write && !err)
+	if (write && !err && left)
 		left -= proc_skip_spaces(&kbuf);
 free:
 	if (write) {