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

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Date:	Thu, 07 Oct 2010 18:59:03 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Américo Wang <xiyou.wangcong@...il.com>,
	Robin Holt <holt@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Willy Tarreau <w@....eu>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	James Morris <jmorris@...ei.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()

Le jeudi 07 octobre 2010 à 09:37 -0700, Eric W. Biederman a écrit :

> The difference between long handling and int handling is a
> usability issue.  I don't expect we will be exporting new
> vectors via sysctl, so the conversion of a handful of vectors
> from int to long is where this is most likely to be used.
> 
> I skimmed through all of what I presume are the current users
> aka linux-2.6.36-rcX and there don't appear to be any users
> of proc_dounlongvec_minmax that use it's vector properties there.
> 
> Which doubly tells me that incrementing the min and max pointers
> is not what we want to do.
> 

Thats fine by me, thanks Eric.

Andrew, please remove previous patch from your tree and replace it by
following one :

[PATCH v2] sysctl: fix min/max handling in __do_proc_doulongvec_minmax()

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"

Fix is to not change min & max pointers in
__do_proc_doulongvec_minmax(), so that all elements of the vector share
an unique min/max limit, like proc_dointvec_minmax().

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 kernel/sysctl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index f88552c..8e45451 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2485,7 +2485,7 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
 		kbuf[left] = 0;
 	}
 
-	for (; left && vleft--; i++, min++, max++, first=0) {
+	for (; left && vleft--; i++, first=0) {
 		unsigned long val;
 
 		if (write) {


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