Subject: Re: WARNING in kernfs_add_one

From: Greg KH <[email-masked]>
Date: Sat, 5 May 2018 09:40:41 -0700

On Sat, May 05, 2018 at 08:47:02AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    8fb11a9a8d51 net/ipv6: rename rt6_next to fib6_next
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=14b27237800000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c416c61f3cd96be
> dashboard link: https://syzkaller.appspot.com/bug?extid=df47f81c226b31d89fb1
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=172fb3e7800000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16552e57800000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: [email-masked]
> 
> RBP: 00007fff808f3e10 R08: 0000000000000002 R09: 00007fff80003534
> R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
> R13: 0000000000000006 R14: 0000000000000000 R15: 0000000000000000
> ------------[ cut here ]------------
> kernfs: ns required in 'ieee80211' for 'phy3'

That's interesting, this looks like a netfilter bug (adding netdev to
the report here.)

Yes, we can "tone down" the kernfs warning to just be an error message
in the log, but there might be something worse going on here.

Network developers, any idea?  Rest of the callback chain is here:

> WARNING: CPU: 0 PID: 4538 at fs/kernfs/dir.c:759 kernfs_add_one+0x406/0x4d0
> fs/kernfs/dir.c:758
> Kernel panic - not syncing: panic_on_warn set ...
> 
> CPU: 0 PID: 4538 Comm: syz-executor486 Not tainted 4.17.0-rc3+ #33
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
>  panic+0x22f/0x4de kernel/panic.c:184
>  __warn.cold.8+0x163/0x1b3 kernel/panic.c:536
>  report_bug+0x252/0x2d0 lib/bug.c:186
>  fixup_bug arch/x86/kernel/traps.c:178 [inline]
>  do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296
>  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
>  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
> RIP: 0010:kernfs_add_one+0x406/0x4d0 fs/kernfs/dir.c:758
> RSP: 0018:ffff8801ca9eece0 EFLAGS: 00010286
> RAX: 000000000000002d RBX: ffffffff87d5cee0 RCX: ffffffff8160ba7d
> RDX: 0000000000000000 RSI: ffffffff81610731 RDI: ffff8801ca9ee840
> RBP: ffff8801ca9eed20 R08: ffff8801d9538500 R09: 0000000000000006
> R10: ffff8801d9538500 R11: 0000000000000000 R12: ffff8801ad1cb6c0
> R13: ffffffff885da640 R14: 0000000000000020 R15: 0000000000000000
>  kernfs_create_link+0x112/0x180 fs/kernfs/symlink.c:41
>  sysfs_do_create_link_sd.isra.2+0x90/0x130 fs/sysfs/symlink.c:43
>  sysfs_do_create_link fs/sysfs/symlink.c:79 [inline]
>  sysfs_create_link+0x65/0xc0 fs/sysfs/symlink.c:91
>  device_add_class_symlinks drivers/base/core.c:1612 [inline]
>  device_add+0x7a0/0x16d0 drivers/base/core.c:1810
>  wiphy_register+0x178a/0x2430 net/wireless/core.c:806
>  ieee80211_register_hw+0x13cd/0x35d0 net/mac80211/main.c:1047
>  mac80211_hwsim_new_radio+0x1d9b/0x3410
> drivers/net/wireless/mac80211_hwsim.c:2772
>  hwsim_new_radio_nl+0x7a7/0xa60 drivers/net/wireless/mac80211_hwsim.c:3246
>  genl_family_rcv_msg+0x889/0x1120 net/netlink/genetlink.c:599
>  genl_rcv_msg+0xc6/0x170 net/netlink/genetlink.c:624
>  netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448
>  genl_rcv+0x28/0x40 net/netlink/genetlink.c:635
>  netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
>  netlink_unicast+0x58b/0x740 net/netlink/af_netlink.c:1336
>  netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901
>  sock_sendmsg_nosec net/socket.c:629 [inline]
>  sock_sendmsg+0xd5/0x120 net/socket.c:639
>  ___sys_sendmsg+0x805/0x940 net/socket.c:2117
>  __sys_sendmsg+0x115/0x270 net/socket.c:2155
>  __do_sys_sendmsg net/socket.c:2164 [inline]
>  __se_sys_sendmsg net/socket.c:2162 [inline]
>  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
>  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4404c9
> RSP: 002b:00007fff808f3e08 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004404c9
> RDX: 0000000000000000 RSI: 0000000020b3dfc8 RDI: 0000000000000005
> RBP: 00007fff808f3e10 R08: 0000000000000002 R09: 00007fff80003534
> R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
> R13: 0000000000000006 R14: 0000000000000000 R15: 0000000000000000
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> Rebooting in 86400 seconds..

Any ideas?

thanks,

greg k-h