From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH -next v2] unix stream: Fix use-after-free crashes
Date: Thu, 08 Sep 2011 15:28:17 +0200
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Cc: "Yan, Zheng" <zheng.z.yan@intel.com>,
	"Yan, Zheng" <yanzheng@21cn.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
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	"Shi, Alex" <alex.shi@intel.com>,
	Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
To: Tim Chen <tim.c.chen@linux.intel.com>
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Le mercredi 07 septembre 2011 =C3=A0 23:26 +0200, Eric Dumazet a =C3=A9=
crit :
> Le mercredi 07 septembre 2011 =C3=A0 05:01 -0700, Tim Chen a =C3=A9cr=
it :

> > Eric, are you planning to do a fast path patch that doesn't do pid =
ref
> > for the case where CONFIG_PID_NS is not set?
> >=20
>=20
> Yes, I'll try to cook a patch.

Thinking a bit more on this issue, I really believe we should not stick
pid/cred in skbs sent from a write() system call.

That would break following use case :

An application uses a write(fd) and expects a receiver using recvmsg()
to get process credentials (SCM_CREDENTIALS)

This is currently working, but not documented (man unix says ancillary
data are sent with sendmsg())

If everybody agrees, I can send a patch for this : This would speedup
write()/read() af_unix by an order of magnitude.