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

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Message-ID: <1315338186.3400.20.camel@edumazet-laptop>
Date:	Tue, 06 Sep 2011 21:43:06 +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>,
	"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>, alex.shi@...el.com
Subject: Re: [PATCH -next v2] unix stream: Fix use-after-free crashes

Le mardi 06 septembre 2011 à 12:33 -0700, Tim Chen a écrit :

> Yes, I think locking the sendmsg for the entire duration of
> unix_stream_sendmsg makes a lot of sense.  It simplifies the logic a lot
> more.  I'll try to cook something up in the next couple of days.

Thats not really possible, we cant hold a spinlock and call
sock_alloc_send_skb() and/or memcpy_fromiovec(), wich might sleep.

You would need to prepare the full skb list, then :
- stick the ref on the last skb of the list.

Transfert the whole skb list in other->sk_receive_queue in one go,
instead of one after another.

Unfortunately, this would break streaming (big send(), and another
thread doing the receive)

Listen, I am wondering why hackbench even triggers SCM code. This is
really odd. We should not have a _single_ pid/cred ref/unref at all.



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