linux-kernel - Re: kernel BUG at net/rxrpc/local

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Message-ID: <CACT4Y+bjLBwVK_6fz2H8fXm0baAVX+vRJ4UbVWG_7yNUO-SOUg@mail.gmail.com>
Date:   Wed, 31 Jul 2019 17:31:45 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     David Howells <dhowells@...hat.com>
Cc:     syzbot <syzbot+1e0edc4b8b7494c28450@...kaller.appspotmail.com>,
        Eric Biggers <ebiggers@...nel.org>,
        David Miller <davem@...emloft.net>,
        linux-afs@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: kernel BUG at net/rxrpc/local_object.c:LINE!

On Wed, Jul 31, 2019 at 5:19 PM David Howells <dhowells@...hat.com> wrote:
>
> Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> > Please send a patch for testing that enables this tracing
> > unconditionally. This should have the same effect. There is no way to
> > hook into a middle of the automated process and arbitrary tune things.
>
> I don't know how to do that off hand.  Do you have an example?

Few messages above I asked it to test:
https://groups.google.com/d/msg/syzkaller-bugs/gEnZkmEWf1s/r2_X_KVQAQAJ

Basically, git repo + branch + patch. Here are the docs:
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches


> Anyway, I think rxrpc_local_processor() is broken with respect to refcounting
> as it gets scheduled when usage==0, but that doesn't stop it being rescheduled
> again by a network packet before it manages to close the UDP socket.
>
> David