unregister_netdevice: waiting for DEV to become free

From: syzbot
Date: Thu Apr 19 2018 - 10:52:06 EST


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)

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.
Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug report.
Note: all commands must start from beginning of the line in the email body.