netdev - Re: [RFC] net: remove erroneous sk null assignment in timestamping

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20111011133411.GA2545@netboy.at.omicron.at>
Date:	Tue, 11 Oct 2011 15:34:11 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [RFC] net: remove erroneous sk null assignment in timestamping

On Sat, Oct 08, 2011 at 12:32:15PM +0200, Johannes Berg wrote:
> On Sat, 2011-10-08 at 10:57 +0200, Eric Dumazet wrote:
> > Check following commit changelog to get some information on this.
> > 
> > commit 2b85a34e911bf483c27cfdd124aeb1605145dc80
> > Author: Eric Dumazet <eric.dumazet@...il.com>
> > Date:   Thu Jun 11 02:55:43 2009 -0700
> > 
> >     net: No more expensive sock_hold()/sock_put() on each tx
...
> There's one thing I still miss though: It seems to me that if you have a
> reference to a socket that has been sk_free()'ed (which is possible
> since it might still have sk_wmem_alloc > 0) you can't sock_hold() that
> socket. That feels a bit unexpected -- and might happen in the code
> Richard just suggested.

Yes, I have been trying to see how to solve this, but it looks like I
am out of luck. 

Even if I use skb_set_owner_w() in skb_clone_tx_timestamp(), still the
sock might go away during skb_orphan() in sock_queue_err_skb().

It is no good to take sock_hold() in skb_complete_tx_timestamp(),
since, as you point out, it might not be safe to call.

So, I wonder, when is it safe to call sock_hold?

Are the 101 odd callers protected against the situation where the last
sock_out() has already happened?

Thanks,

Richard
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html