net/sysctl: use cpumask_parse in flow_limit_cpu_sysctl

cpumask_parse_user works on __user pointers, so this is wrong now.

Fixes: 32927393 ("sysctl: pass kernel pointers to ->proc_handler")
Reported-by: build test robot <lkp@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

net/core/sysctl_net_core.c

@@ -126,7 +126,7 @@ static int flow_limit_cpu_sysctl(struct ctl_table *table, int write,
 		return -ENOMEM;
 
 	if (write) {
-		ret = cpumask_parse_user(buffer, *lenp, mask);
+		ret = cpumask_parse(buffer, mask);
 		if (ret)
 			goto done;