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From:   Jonas Falkevik <jonas.falkevik@gmail.com>
Date:   Wed, 12 Aug 2020 16:19:37 +0200
Message-ID: <CABUN9aDV4yKcoQvMf=griMsx40_tr5sEH9Dod2NnakoC6UwrJg@mail.gmail.com>
Subject: Re: general protection fault in sctp_ulpevent_notify_peer_addr_change
To:     Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc:     syzbot <syzbot+8f2165a7b1f2820feffc@syzkaller.appspotmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-sctp@vger.kernel.org,
        network dev <netdev@vger.kernel.org>,
        Neil Horman <nhorman@tuxdriver.com>,
        syzkaller-bugs@googlegroups.com,
        Vlad Yasevich <vyasevich@gmail.com>,
        Xin Long <lucien.xin@gmail.com>
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On Mon, Aug 10, 2020 at 8:31 PM Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
>
> On Mon, Aug 10, 2020 at 08:37:18AM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    fffe3ae0 Merge tag 'for-linus-hmm' of git://git.kernel.org..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=12f34d3a900000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=50463ec6729f9706
> > dashboard link: https://syzkaller.appspot.com/bug?extid=8f2165a7b1f2820feffc
> > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1517701c900000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11b7e0e2900000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+8f2165a7b1f2820feffc@syzkaller.appspotmail.com
> >
> > general protection fault, probably for non-canonical address 0xdffffc000000004c: 0000 [#1] PREEMPT SMP KASAN
> > KASAN: null-ptr-deref in range [0x0000000000000260-0x0000000000000267]
> > CPU: 0 PID: 12765 Comm: syz-executor391 Not tainted 5.8.0-syzkaller #0
> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> > RIP: 0010:sctp_ulpevent_notify_peer_addr_change+0xa9/0xad0 net/sctp/ulpevent.c:346
>
> Crashed in code added by 45ebf73ebcec ("sctp: check assoc before
> SCTP_ADDR_{MADE_PRIM, ADDED} event"), but it would have crashed a
> couple of instructions later on already anyway.
>
> I can't reproduce this crash, with the same commit and kernel config.
> I'm not seeing how transport->asoc can be null at there.
>
I haven't been able to reproduce this yet either.

Doesn't this report have similarities with "general protection fault
in sctp_ulpevent_nofity_peer_addr_change" from 19 March 2020?
https://syzkaller.appspot.com/bug?extid=3950016bd95c2ca0377b