linux-kernel - Re: possible deadlock in xfrm_policy

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Message-ID: <20200924074204.GA9879@gondor.apana.org.au>
Date:   Thu, 24 Sep 2020 17:42:04 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     peterz@...radead.org
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot <syzbot+c32502fd255cb3a44048@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>
Subject: Re: possible deadlock in xfrm_policy_delete

On Thu, Sep 24, 2020 at 09:30:03AM +0200, peterz@...radead.org wrote:
> On Thu, Sep 24, 2020 at 06:44:12AM +0200, Dmitry Vyukov wrote:
> > On Thu, Sep 24, 2020 at 6:36 AM Herbert Xu <herbert@...dor.apana.org.au> wrote:
> > > >  (k-slock-AF_INET6){+.-.}-{2:2}
> 
> That's a seqlock.

Are you sure? Line 2503 in net/ipv4/tcp.c says

	bh_lock_sock(sk);

> Did that tree you're testing include 267580db047e ("seqlock: Unbreak
> lockdep") ?

According to

https://syzkaller.appspot.com/bug?extid=c32502fd255cb3a44048

the git tree used was

https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/include?id=5fa35f247b563a7893f3f68f19d00ace2ccf3dff

so no it doesn't contain that patch.

Hopefully this would address those seqlock backtraces.  But what
about this particular one which is caused by the socket lock?

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt