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

@@ -45,7 +45,11 @@ static void drop_slab(void)
 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);

kernel/sysctl.c

@@ -117,6 +117,7 @@ static int neg_one = -1;
 static int zero;
 static int __maybe_unused one = 1;
 static int __maybe_unused two = 2;
+static int __maybe_unused three = 3;
 static unsigned long one_ul = 1;
 static int one_hundred = 100;
 #ifdef CONFIG_PRINTK
@@ -971,14 +972,18 @@ static struct ctl_table vm_table[] = {
 		.data		= &sysctl_overcommit_memory,
 		.maxlen		= sizeof(sysctl_overcommit_memory),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &two,
 	},
 	{
 		.procname	= "panic_on_oom",
 		.data		= &sysctl_panic_on_oom,
 		.maxlen		= sizeof(sysctl_panic_on_oom),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &two,
 	},
 	{
 		.procname	= "oom_kill_allocating_task",
@@ -1006,7 +1011,8 @@ static struct ctl_table vm_table[] = {
 		.data		= &page_cluster,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
 	},
 	{
 		.procname	= "dirty_background_ratio",
@@ -1054,7 +1060,8 @@ static struct ctl_table vm_table[] = {
 		.data		= &dirty_expire_interval,
 		.maxlen		= sizeof(dirty_expire_interval),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
 	},
 	{
 		.procname	= "nr_pdflush_threads",
@@ -1130,6 +1137,8 @@ static struct ctl_table vm_table[] = {
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= drop_caches_sysctl_handler,
+		.extra1		= &one,
+		.extra2		= &three,
 	},
 #ifdef CONFIG_COMPACTION
 	{