netdev - Re: [Security] [SECURITY] Fix leaking of kernel heap addresses via /proc

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Date:	Mon, 08 Nov 2010 08:33:32 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	andi@...stfloor.org, drosenberg@...curity.com,
	chas3@...rs.sourceforge.net, tytso@....edu,
	torvalds@...ux-foundation.org, kuznet@....inr.ac.ru,
	pekkas@...core.fi, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net, remi.denis-courmont@...ia.com,
	netdev@...r.kernel.org, security@...nel.org
Subject: Re: [Security] [SECURITY] Fix leaking of kernel heap addresses via
 /proc

Le dimanche 07 novembre 2010 à 18:01 -0800, David Miller a écrit :
> From: Andi Kleen <andi@...stfloor.org>
> Date: Mon, 8 Nov 2010 00:56:10 +0100
> 
> > I would just remove the pointers from /proc and supply 
> > gdb macros that extract the equivalent information from /proc/kcore.
> > This is a bit racy, but for debugging it should be no
> > problem to run them multiple times as needed.
> 
> I do not think at all that this is tenable for the kind of
> things people use the socket pointers for when debugging
> problems.
> 
> I defeinitely prefer the inode number to this idea.

We currently have no guarantee of sockets inode numbers unicity.
I admit chances of clash are low.

When a printk() happens right before a BUG(), how are we going to check
the dumped registers are possibly close the socket involved, if we dont
have access to the machine, and only the crashlog ?

BTW, any local user can look at "dmesg", and crash reports. These
reports are even published on a remote site (bugzilla) so that hostile
hackers can be feeded.

I am OK to delete socket pointers from /proc files for non root users
(after checking things like lsof continue to work correctly).
I dont remember using them while doing debugging stuff.

BTW, rtnetlink also expose socket pointers to non root users :

$ ss -e dst 192.168.20.108
State      Recv-Q Send-Q    Local Address:Port    Peer Address:Port   
ESTAB      0      0         10.150.51.210:46979   192.168.20.108:ssh 
timer:(keepalive,119min,0) ino:136919 sk:ffff88002129d7c0

Mixing in same patch /proc pointers removal and printk() pointers
removal seems wrong to me. Very different problems.

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