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From: David Laight <David.Laight@ACULAB.COM>
To: "'Linus Torvalds'" <torvalds@linux-foundation.org>,
	Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: David Herrmann <dh.herrmann@gmail.com>, Willy Tarreau <w@1wt.eu>,
	"David S. Miller" <davem@davemloft.net>,
	netdev <netdev@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	???? ????????? <socketpair@gmail.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Simon McVittie <simon.mcvittie@collabora.co.uk>
Subject: RE: [PATCH v2] unix: properly account for FDs passed over unix sockets
Date: Wed, 3 Feb 2016 12:19:11 +0000	[thread overview]
Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CCD516C@AcuExch.aculab.com> (raw)
In-Reply-To: <CA+55aFz0CXGexEBmb8JU0+w7sFf3VfE3TpRzdj3aTiDxg2zDpg@mail.gmail.com>

From: Linus Torvalds
> Sent: 02 February 2016 20:45
> On Tue, Feb 2, 2016 at 12:32 PM, Hannes Frederic Sowa
> <hannes@stressinduktion.org> wrote:
> >
> > Unfortunately we never transfer a scm_cookie via the skbs but merely use it
> > to initialize unix_skb_parms structure in skb->cb and destroy it afterwards.
> 
> Ok, I obviously didn't check very closely.
> 
> > But "struct pid *" in unix_skb_parms should be enough to get us to
> > corresponding "struct cred *" so we can decrement the correct counter during
> > skb destruction.
> 
> Umm. I think the "struct cred" may change in between, can't it?
> 
> So I don't think you can later look up the cred based on the pid.
> 
> Could we add the cred pointer (or just the user pointer) to the unix_skb_parms?
> 
> Or maybe just add it to the "struct scm_fp_list"?

Is that going to work if the sending process exits before the message is read?
You need a reference count against the structure than contains the count.
I think this is 'struct user' not 'struct cred'

	David

  parent reply	other threads:[~2016-02-03 12:22 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-10  6:54 [PATCH v2] unix: properly account for FDs passed over unix sockets Willy Tarreau
2016-01-10  6:58 ` Willy Tarreau
2016-01-11  5:05 ` David Miller
2016-02-02 17:34 ` David Herrmann
2016-02-02 18:29   ` Hannes Frederic Sowa
2016-02-02 19:29     ` Linus Torvalds
2016-02-02 20:32       ` Hannes Frederic Sowa
2016-02-02 20:39         ` Willy Tarreau
2016-02-02 21:55           ` Hannes Frederic Sowa
     [not found]             ` <CA+55aFzqdR80MKupCs+va8vtbTU67Jobax1QAbfWNktQCXFxpA@mail.gmail.com>
2016-02-03  0:57               ` Hannes Frederic Sowa
2016-02-03  1:12                 ` Hannes Frederic Sowa
2016-02-02 20:44         ` Linus Torvalds
2016-02-02 20:49           ` Willy Tarreau
2016-02-02 20:53             ` Linus Torvalds
2016-02-02 20:58               ` Willy Tarreau
2016-02-02 20:56           ` Hannes Frederic Sowa
2016-02-03 12:19           ` David Laight [this message]
2016-02-03 11:36   ` Simon McVittie
2016-02-03 11:56     ` Hannes Frederic Sowa
2016-02-03 11:56     ` David Herrmann
2016-02-03 12:49       ` Simon McVittie
2016-02-03 14:07       ` Hannes Frederic Sowa
2016-01-10  6:58 Willy Tarreau

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