hugetlb: do not allow pagesize >= MAX_ORDER pool adjustment

Huge pages with order >= MAX_ORDER must be allocated at boot via the
kernel command line, they cannot be allocated or freed once the kernel is
up and running.  Currently we allow values to be written to the sysfs and
sysctl files controling pool size for these huge page sizes.  This patch
makes the store functions for nr_hugepages and nr_overcommit_hugepages
return -EINVAL when the pool for a page size >= MAX_ORDER is changed.

[akpm@linux-foundation.org: avoid multiple return paths in nr_hugepages_store_common()]
[caiqian@redhat.com: add checking in hugetlb_overcommit_handler()]
Signed-off-by: Eric B Munson <emunson@mgebm.net>
Reported-by: CAI Qian <caiqian@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -1363,6 +1363,7 @@ static ssize_t nr_hugepages_show_common(struct kobject *kobj,
 
 	return sprintf(buf, "%lu\n", nr_huge_pages);
 }
+
 static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
 			struct kobject *kobj, struct kobj_attribute *attr,
 			const char *buf, size_t len)
@@ -1375,11 +1376,16 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
 
 	err = strict_strtoul(buf, 10, &count);
 	if (err) {
-		NODEMASK_FREE(nodes_allowed);
-		return 0;
+		err = 0;		/* This seems wrong */
+		goto out;
 	}
 
 	h = kobj_to_hstate(kobj, &nid);
+	if (h->order >= MAX_ORDER) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	if (nid == NUMA_NO_NODE) {
 		/*
 		 * global hstate attribute
@@ -1405,6 +1411,9 @@ static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
 		NODEMASK_FREE(nodes_allowed);
 
 	return len;
+out:
+	NODEMASK_FREE(nodes_allowed);
+	return err;
 }
 
 static ssize_t nr_hugepages_show(struct kobject *kobj,
@@ -1447,6 +1456,7 @@ static ssize_t nr_overcommit_hugepages_show(struct kobject *kobj,
 	struct hstate *h = kobj_to_hstate(kobj, NULL);
 	return sprintf(buf, "%lu\n", h->nr_overcommit_huge_pages);
 }
+
 static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
 		struct kobj_attribute *attr, const char *buf, size_t count)
 {
@@ -1454,6 +1464,9 @@ static ssize_t nr_overcommit_hugepages_store(struct kobject *kobj,
 	unsigned long input;
 	struct hstate *h = kobj_to_hstate(kobj, NULL);
 
+	if (h->order >= MAX_ORDER)
+		return -EINVAL;
+
 	err = strict_strtoul(buf, 10, &input);
 	if (err)
 		return 0;
@@ -1864,6 +1877,9 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
 	if (!write)
 		tmp = h->max_huge_pages;
 
+	if (write && h->order >= MAX_ORDER)
+		return -EINVAL;
+
 	table->data = &tmp;
 	table->maxlen = sizeof(unsigned long);
 	ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
@@ -1927,6 +1943,9 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
 	if (!write)
 		tmp = h->nr_overcommit_huge_pages;
 
+	if (write && h->order >= MAX_ORDER)
+		return -EINVAL;
+
 	table->data = &tmp;
 	table->maxlen = sizeof(unsigned long);
 	ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);