netdev - Re: [PATCH] sysfs: Don't allow the creation of symlinks we can't remove

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Date:	Thu, 22 Jul 2010 12:10:34 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Greg KH <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>,
	Kay Sievers <kay.sievers@...y.org>, Greg KH <greg@...ah.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] sysfs: Don't allow the creation of symlinks we can't
 remove

On Thu, 2010-07-22 at 03:05 -0700, Eric W. Biederman wrote:

> >> Detect this problem up front and simply don't create symlinks we won't
> >> be able to remove later.  This prevents symlink leakage and fails in
> >> a much clearer and more understandable way.
> >
> > Eric, I was looking into sysfs netns support for wireless, and with this
> > patch applied I just get the warning and no network interfaces.
> 
> The warning patch just makes things fail faster.  Although I get some of the
> wireless interfaces for hwsim when I use this one.

Hmm, I didn't.

> > Was there any patch that was supposed to fix hwsim?
> 
> - If you have my patches that fix CONFIG_SYSFS_DEPRECATED,
>   you should find everything works there.

But then I was carrying those two patches too.

> As for a proper fix I have just resent my one liner to
> drives/base/core.c I can't think of a better option right now.
> 
> For hwsim it is arguable, but the behaviour of sysfs for the
> bluetooth bnep driver is very clearly a 3 year old regression,
> and the cause is exactly the same.

Right, it actually starts working again with that patch you sent.
However, netns support is really broken:

<create net namespace, put phy0/wlan0 into it>

root@kvm:~# ip link
3: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 02:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
7: lo: <LOOPBACK> mtu 16436 qdisc noop state DOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
root@kvm:~# ls /sys/class/net/
eth0  hwsim0  lo  wlan1  wlan2

johannes

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