From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH] sysctl: fix min/max handling in
 __do_proc_doulongvec_minmax()
Date: Thu, 07 Oct 2010 11:51:21 +0200
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Cc: Robin Holt <holt@sgi.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Willy Tarreau <w@1wt.eu>,
	"David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
	James Morris <jmorris@namei.org>,
	"Pekka Savola (ipv6)" <pekkas@netcore.fi>,
	Patrick McHardy <kaber@trash.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>, ebiederm@xmission.com
To: =?ISO-8859-1?Q?Am=E9rico?= Wang <xiyou.wangcong@gmail.com>
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Le jeudi 07 octobre 2010 =C3=A0 17:25 +0800, Am=C3=A9rico Wang a =C3=A9=
crit :
> >>
> >
> >Here is the final one.
>=20
> Oops, that one is not correct. Hopefully this one
> is correct.
>=20
> --------------->
>=20
> Eric D. noticed that we may trigger an OOPS if we leave ->extra{1,2}
> to NULL when we use proc_doulongvec_minmax().
>=20
> Actually, we don't need to store min/max values in a vector,
> because all the elements in the vector should share the same min/max
> value, like what proc_dointvec_minmax() does.
>=20

If we assert same min/max limits are to be applied to all elements,
a much simpler fix than yours would be :

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] =3D 0;
 	}
=20
-	for (; left && vleft--; i++, min++, max++, first=3D0) {
+	for (; left && vleft--; i++, first=3D0) {
 		unsigned long val;
=20
 		if (write) {


Please dont send huge patches like this to 'fix' a bug,
especially on slow path.

=46irst we fix the bug, _then_ we can try to make code more=20
efficient or more pretty or shorter.

So the _real_ question is :

Should the min/max limits should be a single pair,
shared by all elements, or a vector of limits.