From: Dmitry Vyukov <dvyukov@google.com>
To: syzkaller <syzkaller@googlegroups.com>
Cc: Richard Guy Briggs <rgb@redhat.com>,
linux-audit@redhat.com, Paul Moore <pmoore@redhat.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>
Subject: Re: netlink: GPF in sock_sndtimeo
Date: Mon, 12 Dec 2016 11:07:41 +0100 [thread overview]
Message-ID: <CACT4Y+Yn0ZUv0=g4t5BYQC5tUqqmNFreUyB3nw=vx1GXEn1NSQ@mail.gmail.com> (raw)
In-Reply-To: <CAM_iQpVcHGywXn90EpiSz-LsUDgKVqs-7BY-L7UBCu2VxkC31Q@mail.gmail.com>
On Sat, Dec 10, 2016 at 8:40 AM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
>>> On 2016-12-08 22:57, Cong Wang wrote:
>>>> 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.
>>>
>>> This is what I expected and why I originally added the mutex lock in the
>>> callback... The dumps I got were bare with no wrapper identifying the
>>> process context or specific error, so I'm at a bit of a loss how to
>>> solve this (without thinking more about it) other than instinctively
>>> removing the mutex.
>>
>> Netlink notifier can safely be converted to blocking one, I will send
>> a patch.
>>
>> But I seriously doubt you really need NETLINK_URELEASE here,
>> it adds nothing but overhead, b/c the netlink notifier is called on
>> every netlink socket in the system, but for net exit path, that is
>> relatively a slow path.
>>
>> Also, kauditd_send_skb() needs audit_cmd_mutex too.
>
> Please let me know what you think about the attached patch?
Applied the patch locally and have not seen the bug since then (~24
hours of testing).
next prev parent reply other threads:[~2016-12-12 10:08 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
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 [this message]
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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