[S390] dasd: use vmalloc for statistics input buffer

The size of the buffer that is used to store DASD statistics input
strings depends on the user input. If the input string is to large,
the write operation could fail with -ENOMEM. To avoid this, use
vmalloc instead of kmalloc.

Signed-off-by: Stefan Weinhuber <wein@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/drivers/s390/block/dasd_proc.c b/drivers/s390/block/dasd_proc.c
index 6c3c536..e12989f 100644
--- a/drivers/s390/block/dasd_proc.c
+++ b/drivers/s390/block/dasd_proc.c
@@ -312,14 +312,14 @@
 		pr_info("The statistics have been reset\n");
 	} else
 		goto out_parse_error;
-	kfree(buffer);
+	vfree(buffer);
 	return user_len;
 out_parse_error:
 	rc = -EINVAL;
 	pr_warning("%s is not a supported value for /proc/dasd/statistics\n",
 		str);
 out_error:
-	kfree(buffer);
+	vfree(buffer);
 	return rc;
 #else
 	pr_warning("/proc/dasd/statistics: is not activated in this kernel\n");