Re: unregister_netdevice: waiting for DEV to become free

[Dmitry Vyukov]

On Thu, Apr 19, 2018 at 4:52 PM, syzbot
<syzbot+2dfb68e639f0621b19fb@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> 87ef12027b9b1dd0e0b12cf311fbcb19f9d92539 (Wed Apr 18 19:48:17 2018 +0000)
> Merge tag 'ceph-for-4.17-rc2' of git://github.com/ceph/ceph-client
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=2dfb68e639f0621b19fb
>
> So far this crash happened 5 times on upstream.
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5531107864870912
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=1808800213120130118
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)

There are 2 reproducers for these hangs (presumably for different bugs):

https://groups.google.com/d/msg/syzkaller/-06_laheMF0/4wfWs6ATBwAJ
https://groups.google.com/d/msg/syzkaller/-06_laheMF0/MxCjIiHkBwAJ

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+2dfb68e639f0621b19fb@xxxxxxxxxxxxxxxxxxxxxxxxx
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
> connbytes_mt_check: 1 callbacks suppressed
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> unregister_netdevice: waiting for lo to become free. Usage count = 3
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> kernel msg: ebtables bug: please report to author: Entries_size never zero
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> nla_parse: 1 callbacks suppressed
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
> netlink: 17 bytes leftover after parsing attributes in process
> `syz-executor6'.
> xt_connbytes: cannot load conntrack support for proto=7
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
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