netdev - Re: [PATCH] sysctl: fix min/max handling in __do_proc_doulongvec

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Date:	Mon, 4 Oct 2010 11:09:15 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Robin Holt <holt@....com>, Willy Tarreau <w@....eu>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	"Pekka Savola (ipv6)" <pekkas@...core.fi>,
	Patrick McHardy <kaber@...sh.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>
Subject: Re: [PATCH] sysctl: fix min/max handling in
 __do_proc_doulongvec_minmax()

On Sat, Oct 02, 2010 at 03:17:49PM +0200, Eric Dumazet wrote:
>When proc_doulongvec_minmax() is used with an array of longs,
>and no min/max check requested (.extra1 or .extra2 being NULL), we
>dereference a NULL pointer for the second element of the array.
>
>Noticed while doing some changes in network stack for the "16TB problem"
>
>Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
>---
> kernel/sysctl.c |    3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/kernel/sysctl.c b/kernel/sysctl.c
>index f88552c..4fba86d 100644
>--- a/kernel/sysctl.c
>+++ b/kernel/sysctl.c
>@@ -2500,7 +2500,8 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
> 				break;
> 			if (neg)
> 				continue;
>-			if ((min && val < *min) || (max && val > *max))
>+			if ((table->extra1 && val < *min) ||
>+			    (table->extra2 && val > *max))
> 				continue;


Yes? This is wrong for me, min and max are pointers to ->extra{1,2},
they are increased within the for loop, you are only checking the
the pointer to the first element of ->extra{1,2}.
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