s390/topology: correct topology mode proc handler

Reuse proc_douintvec_minmax to simplify topology mode proc handler.
This also enforces correct range of 0-1 on proc writes and correctly
handles numbers starting with 0 or spaces.

Before:
$ echo 01 > /proc/sys/s390/topology
$ cat /proc/sys/s390/topology
0
$ echo ' 1' > /proc/sys/s390/topology
-bash: echo: write error: Invalid argument
$ echo 2 > /proc/sys/s390/topology
-bash: echo: write error: Invalid argument
$ echo 12 > /proc/sys/s390/topology
$ cat /proc/sys/s390/topology
1

After:
$ echo 01 > /proc/sys/s390/topology
$ cat /proc/sys/s390/topology
1
$ echo ' 1' > /proc/sys/s390/topology
$ cat /proc/sys/s390/topology
1
$ echo 2 > /proc/sys/s390/topology
-bash: echo: write error: Invalid argument
$ echo 12 > /proc/sys/s390/topology
-bash: echo: write error: Invalid argument
$ echo '   0' > /proc/sys/s390/topology
$ cat /proc/sys/s390/topology
0

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 18 insertions, 25 deletions

diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index 33ebb423c613..e8184a15578a 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -579,40 +579,33 @@ early_param("topology", topology_setup);
 static int topology_ctl_handler(struct ctl_table *ctl, int write,
                                 void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-        unsigned int len;
+        int enabled = topology_is_enabled();
         int new_mode;
-        char buf[2];
+        int zero = 0;
+        int one = 1;
+        int rc;
+        struct ctl_table ctl_entry = {
+                .procname       = ctl->procname,
+                .data           = &enabled,
+                .maxlen         = sizeof(int),
+                .extra1         = &zero,
+                .extra2         = &one,
+        };
+
+        rc = proc_douintvec_minmax(&ctl_entry, write, buffer, lenp, ppos);
+        if (rc < 0 || !write)
+                return rc;
 
-        if (!*lenp || *ppos) {
-                *lenp = 0;
-                return 0;
-        }
-        if (!write) {
-                memcpy(buf, topology_is_enabled() ? "1\n" : "0\n", ARRAY_SIZE(buf));
-                len = strnlen(buf, ARRAY_SIZE(buf));
-                if (len > *lenp)
-                        len = *lenp;
-                if (copy_to_user(buffer, buf, len))
-                        return -EFAULT;
-                goto out;
-        }
-        len = *lenp;
-        if (copy_from_user(buf, buffer, len > sizeof(buf) ? sizeof(buf) : len))
-                return -EFAULT;
-        if (buf[0] != '0' && buf[0] != '1')
-                return -EINVAL;
         mutex_lock(&smp_cpu_state_mutex);
-        new_mode = topology_get_mode(buf[0] == '1');
+        new_mode = topology_get_mode(enabled);
         if (topology_mode != new_mode) {
                 topology_mode = new_mode;
                 topology_schedule_update();
         }
         mutex_unlock(&smp_cpu_state_mutex);
         topology_flush_work();
-out:
-        *lenp = len;
-        *ppos += len;
-        return 0;
+
+        return rc;
 }
 
 static struct ctl_table topology_ctl_table[] = {