Re: [syzbot] INFO: trying to register non-static key in __timer_delete_sync

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
unregister_netdevice: waiting for DEV to become free

unregister_netdevice: waiting for lo to become free. Usage count = 2
leaked reference.
 __netdev_tracker_alloc include/linux/netdevice.h:4039 [inline]
 netdev_hold include/linux/netdevice.h:4068 [inline]
 ipv6_add_dev+0x43e/0x1320 net/ipv6/addrconf.c:401
 addrconf_notify+0x61e/0x18c0 net/ipv6/addrconf.c:3552
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:87
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1945
 call_netdevice_notifiers_extack net/core/dev.c:1983 [inline]
 call_netdevice_notifiers net/core/dev.c:1997 [inline]
 register_netdevice+0xfb4/0x1640 net/core/dev.c:10084
 register_netdev+0x31/0x50 net/core/dev.c:10179
 loopback_net_init+0x7a/0x170 drivers/net/loopback.c:219
 ops_init+0xb9/0x670 net/core/net_namespace.c:135
 setup_net+0x793/0xe60 net/core/net_namespace.c:333
 copy_net_ns+0x31b/0x6b0 net/core/net_namespace.c:483
 create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xc5/0x1f0 kernel/nsproxy.c:228
 ksys_unshare+0x449/0x920 kernel/fork.c:3202
 __do_sys_unshare kernel/fork.c:3273 [inline]
 __se_sys_unshare kernel/fork.c:3271 [inline]
 __x64_sys_unshare+0x31/0x40 kernel/fork.c:3271
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd


Tested on:

commit:         75da437a Merge branch '40GbE' of git://git.kernel.org/..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=16527cc7480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6e5fc864153bbc8c
dashboard link: https://syzkaller.appspot.com/bug?extid=1e164be619b690a43d79
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10692a4f480000