sysctl: add some missing input constraint checks

Add boundaries of allowed input ranges for: dirty_expire_centisecs,
drop_caches, overcommit_memory, page-cluster and panic_on_oom.

Signed-off-by: Petr Holasek <pholasek@redhat.com>
Acked-by: Dave Young <hidave.darkstar@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/drop_caches.c

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index 2195c21..816f88e 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -45,7 +45,11 @@
 int drop_caches_sysctl_handler(ctl_table *table, int write,
 	void __user *buffer, size_t *length, loff_t *ppos)
 {
-	proc_dointvec_minmax(table, write, buffer, length, ppos);
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
+	if (ret)
+		return ret;
 	if (write) {
 		if (sysctl_drop_caches & 1)
 			iterate_supers(drop_pagecache_sb, NULL);