From: Rainer Weikusat <rweikusat@mobileactivedefense•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: Rainer Weikusat <rweikusat@mobileactivedefense•com>,
Jason Baron <jbaron@akamai•com>,
davem@davemloft•net, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org, minipli@googlemail•com,
normalperson@yhbt•net, viro@zeniv•linux.org.uk,
davidel@xmailserver•org, dave@stgolabs•net, olivier@mauras•ch,
pageexec@freemail•hu, torvalds@linux-foundation•org,
peterz@infradead•org
Subject: Re: [PATCH v2 1/3] unix: fix use-after-free in unix_dgram_poll()
Date: Mon, 05 Oct 2015 18:20:45 +0100 [thread overview]
Message-ID: <8737xpxmdu.fsf@doppelsaurus.mobileactivedefense.com> (raw)
In-Reply-To: <1444064074.9555.4.camel@edumazet-glaptop2.roam.corp.google.com> (Eric Dumazet's message of "Mon, 05 Oct 2015 09:54:34 -0700")
Eric Dumazet <eric.dumazet@gmail•com> writes:
> On Mon, 2015-10-05 at 17:31 +0100, Rainer Weikusat wrote:
>
>> atomic_long_set(&u->inflight, 0);
>> INIT_LIST_HEAD(&u->link);
>> @@ -2135,8 +2139,16 @@ static unsigned int unix_poll(struct fil
>> static unsigned int unix_dgram_poll(struct file *file, struct socket *sock,
>> poll_table *wait)
>> {
>> - struct sock *sk = sock->sk, *other;
>> - unsigned int mask, writable;
>> + struct sock *sk = sock->sk, *other, *pp;
>> + struct unix_sock *u;
>> + unsigned int mask, writable, dead;
>> +
>> + u = unix_sk(sk);
>> + pp = u->poll_peer;
>> + if (pp) {
>> + u->poll_peer = NULL;
>> + sock_put(pp);
>> + }
>
>
> This looks racy.
> Multiple threads could use poll() at the same time,
> and you would have too many sock_put()
That's one of the reasons why I wrote "might work": The use of a single
structure member without any locking for the sock_poll_wait suggests
that this is taken care of in some other way, as does the absence of any
comment about that in the 'public' LDDs ("Linux Device Drivers"),
however, I don't really know if this is true. If not, this simple idea
can't work.
next prev parent reply other threads:[~2015-10-05 17:22 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-02 20:43 [PATCH v2 0/3] af_unix: fix use-after-free Jason Baron
2015-10-02 20:43 ` [PATCH v2 1/3] unix: fix use-after-free in unix_dgram_poll() Jason Baron
2015-10-03 5:46 ` Mathias Krause
2015-10-03 17:02 ` Rainer Weikusat
2015-10-04 17:41 ` Rainer Weikusat
2015-10-05 16:31 ` Rainer Weikusat
2015-10-05 16:54 ` Eric Dumazet
2015-10-05 17:20 ` Rainer Weikusat [this message]
2015-10-05 17:55 ` Jason Baron
2015-10-12 20:41 ` Rainer Weikusat
2015-10-14 3:44 ` Jason Baron
2015-10-14 17:47 ` Rainer Weikusat
2015-10-15 2:54 ` Jason Baron
2015-10-18 20:58 ` Rainer Weikusat
2015-10-19 15:07 ` Jason Baron
2015-10-20 22:29 ` Rainer Weikusat
2015-10-21 17:34 ` Rainer Weikusat
2015-10-28 16:46 ` [RFC] " Rainer Weikusat
2015-10-28 17:57 ` Jason Baron
2015-10-29 14:23 ` Rainer Weikusat
2015-10-30 20:52 ` [RFC] unix: fix use-after-free in unix_dgram_poll()/ 4.2.5 Rainer Weikusat
[not found] ` <57d2f5b6aae251957bff7a1a52b8bf2c@core-hosting.net>
2015-11-02 21:55 ` Rainer Weikusat
2015-10-02 20:43 ` [PATCH v2 2/3] af_unix: Convert gc_flags to flags Jason Baron
2015-10-02 20:44 ` [PATCH v2 3/3] af_unix: optimize the unix_dgram_recvmsg() Jason Baron
2015-10-05 7:41 ` Peter Zijlstra
2015-10-05 17:13 ` Jason Baron
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