From: Cong Wang <xiyou.wangcong@gmail.com>
To: Richard Guy Briggs <rgb@redhat.com>
Cc: linux-audit@redhat.com, Paul Moore <pmoore@redhat.com>,
Dmitry Vyukov <dvyukov@google.com>,
David Miller <davem@davemloft.net>,
Johannes Berg <johannes.berg@intel.com>,
Florian Westphal <fw@strlen.de>,
Eric Dumazet <edumazet@google.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
netdev <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: netlink: GPF in sock_sndtimeo
Date: Thu, 8 Dec 2016 22:57:18 -0800 [thread overview]
Message-ID: <CAM_iQpWRe0tDk=wvXONG7hamH3EtE0nJuAOF1kVKJgdpMvz2DA@mail.gmail.com> (raw)
In-Reply-To: <20161209060248.GT22655@madcap2.tricolour.ca>
On Thu, Dec 8, 2016 at 10:02 PM, Richard Guy Briggs <rgb@redhat.com> wrote:
> I also tried to extend Cong Wang's idea to attempt to proactively respond to a
> NETLINK_URELEASE on the audit_sock and reset it, but ran into a locking error
> stack dump using mutex_lock(&audit_cmd_mutex) in the notifier callback.
> Eliminating the lock since the sock is dead anways eliminates the error.
>
> Is it safe? I'll resubmit if this looks remotely sane. Meanwhile I'll try to
> get the test case to compile.
It doesn't look safe, because 'audit_sock', 'audit_nlk_portid' and 'audit_pid'
are updated as a whole and race between audit_receive_msg() and
NETLINK_URELEASE.
> @@ -1167,10 +1190,14 @@ static void __net_exit audit_net_exit(struct net *net)
> {
> struct audit_net *aunet = net_generic(net, audit_net_id);
> struct sock *sock = aunet->nlsk;
> +
> + mutex_lock(&audit_cmd_mutex);
> if (sock == audit_sock) {
> audit_pid = 0;
> + audit_nlk_portid = 0;
> audit_sock = NULL;
> }
> + mutex_unlock(&audit_cmd_mutex);
>
If you decide to use NETLINK_URELEASE notifier, the above piece is no
longer needed, the net_exit path simply releases a refcnt.
next prev parent reply other threads:[~2016-12-09 6:57 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CACT4Y+aG1+91U1PWMTwpE_6vbEuqG7CdLCM1H=3WVJWtz=>
[not found] ` <CAM_iQpVeLvfYV+1jX1ZKOntZim4roof4=>
2016-11-29 16:48 ` netlink: GPF in sock_sndtimeo Richard Guy Briggs
2016-11-29 23:13 ` Cong Wang
2016-11-30 4:52 ` Richard Guy Briggs
2016-12-09 6:02 ` Richard Guy Briggs
2016-12-09 6:57 ` Cong Wang [this message]
2016-12-09 11:01 ` Richard Guy Briggs
2016-12-10 4:13 ` Cong Wang
2016-12-10 7:40 ` Cong Wang
2016-12-12 10:07 ` Dmitry Vyukov
2016-12-13 7:51 ` Richard Guy Briggs
2016-12-13 8:28 ` Richard Guy Briggs
2016-12-12 10:02 ` Richard Guy Briggs
2016-12-12 10:03 ` [PATCH v2] audit: use proper refcount locking on audit_sock Richard Guy Briggs
2016-12-12 17:10 ` Paul Moore
2016-12-13 4:49 ` Richard Guy Briggs
2016-12-12 20:18 ` Paul Moore
2016-12-13 5:10 ` Richard Guy Briggs
2016-12-13 15:01 ` Richard Guy Briggs
2016-12-12 23:58 ` Cong Wang
2016-12-13 14:55 ` Richard Guy Briggs
2016-12-13 0:10 ` netlink: GPF in sock_sndtimeo Cong Wang
2016-12-13 10:52 ` Richard Guy Briggs
2016-12-14 0:17 ` Cong Wang
2016-12-14 4:17 ` Richard Guy Briggs
2016-12-13 15:03 ` [RFC PATCH v3] audit: use proper refcount locking on audit_sock Richard Guy Briggs
2016-12-13 20:50 ` Paul Moore
2016-12-14 0:19 ` Cong Wang
2016-12-14 4:00 ` Richard Guy Briggs
2016-12-14 5:36 ` Cong Wang
2016-12-09 10:49 ` netlink: GPF in sock_sndtimeo Dmitry Vyukov
2016-12-09 11:48 ` Richard Guy Briggs
2016-12-09 11:53 ` Dmitry Vyukov
2016-12-09 12:12 ` Richard Guy Briggs
2016-11-26 15:44 Dmitry Vyukov
2016-11-26 16:17 ` Eric Dumazet
2016-11-27 1:11 ` Cong Wang
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