netdev - Re: [PATCH -next v2] unix stream: Fix use-after-free crashes

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Message-ID: <1315488497.2456.21.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Thu, 08 Sep 2011 15:28:17 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	"Yan, Zheng" <zheng.z.yan@...el.com>,
	"Yan, Zheng" <yanzheng@...n.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
	"jirislaby@...il.com" <jirislaby@...il.com>,
	"sedat.dilek@...il.com" <sedat.dilek@...il.com>,
	"Shi, Alex" <alex.shi@...el.com>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>
Subject: Re: [PATCH -next v2] unix stream: Fix use-after-free crashes

Le mercredi 07 septembre 2011 à 23:26 +0200, Eric Dumazet a écrit :
> Le mercredi 07 septembre 2011 à 05:01 -0700, Tim Chen a écrit :

> > 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?
> > 
> 
> 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.



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