From 70da2340fbc68e91e701762f785479ab495a0869 Mon Sep 17 00:00:00 2001
From: Amerigo Wang <amwang@redhat.com>
Date: Mon, 14 Dec 2009 17:59:52 -0800
Subject: [PATCH] 'sysctl_max_map_count' should be non-negative

Jan Engelhardt reported we have this problem:

setting max_map_count to a value large enough results in programs dying at
first try.  This is on 2.6.31.6:

15:59 borg:/proc/sys/vm # echo $[1<<31-1] >max_map_count
15:59 borg:/proc/sys/vm # cat max_map_count
1073741824
15:59 borg:/proc/sys/vm # echo $[1<<31] >max_map_count
15:59 borg:/proc/sys/vm # cat max_map_count
Killed

This is because we have a chance to make 'max_map_count' negative.  but
it's meaningless.  Make it only accept non-negative values.

Reported-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: James Morris <jmorris@namei.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 kernel/sysctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 60fc93131095..45e4bef0012a 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1131,7 +1131,8 @@ static struct ctl_table vm_table[] = {
 		.data		= &sysctl_max_map_count,
 		.maxlen		= sizeof(sysctl_max_map_count),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec,
+		.extra1		= &zero,
 	},
 #else
 	{