possible deadlock in dev_mc_unsync

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b835a71e usbnet: smsc95xx: Fix use-after-free after removal
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=16e25419100000
kernel config: https://syzkaller.appspot.com/x/.config?x=dcc6334acae363d4
dashboard link: https://syzkaller.appspot.com/bug?extid=08e3d39f3eb8643216be
compiler: gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+08e3d3...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
5.8.0-rc1-syzkaller #0 Not tainted
--------------------------------------------
syz-executor.5/12181 is trying to acquire lock:
ffff888090564280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: netif_addr_lock_nested include/linux/netdevice.h:4243 [inline]
ffff888090564280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync net/core/dev_addr_lists.c:915 [inline]
ffff888090564280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync+0xf4/0x190 net/core/dev_addr_lists.c:909

but task is already holding lock:
ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:358 [inline]
ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: netif_addr_lock_bh include/linux/netdevice.h:4248 [inline]
ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync net/core/dev_addr_lists.c:914 [inline]
ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync+0xb0/0x190 net/core/dev_addr_lists.c:909

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&vlan_netdev_addr_lock_key/1);
lock(&vlan_netdev_addr_lock_key/1);

*** DEADLOCK ***

May be due to missing lock nesting notation

6 locks held by syz-executor.5/12181:
#0: ffffffff8a809730 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:763
#1: ffffffff8a8097e8 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
#1: ffffffff8a8097e8 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x76a/0x9e0 net/netlink/genetlink.c:751
#2: ffffffff8a7d1088 (devlink_mutex){+.+.}-{3:3}, at: devlink_nl_pre_doit+0x27/0x6a0 net/core/devlink.c:401
#3: ffff88809df48370 (&nsim_dev->port_list_lock){+.+.}-{3:3}, at: nsim_dev_port_del_all drivers/net/netdevsim/dev.c:951 [inline]
#3: ffff88809df48370 (&nsim_dev->port_list_lock){+.+.}-{3:3}, at: nsim_dev_reload_destroy+0x9e/0x1e0 drivers/net/netdevsim/dev.c:1130
#4: ffffffff8a7afda8 (rtnl_mutex){+.+.}-{3:3}, at: nsim_destroy+0x2b/0x60 drivers/net/netdevsim/netdev.c:329
#5: ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:358 [inline]
#5: ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: netif_addr_lock_bh include/linux/netdevice.h:4248 [inline]
#5: ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync net/core/dev_addr_lists.c:914 [inline]
#5: ffff88805dd76280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync+0xb0/0x190 net/core/dev_addr_lists.c:909

stack backtrace:
CPU: 1 PID: 12181 Comm: syz-executor.5 Not tainted 5.8.0-rc1-syzkaller #0
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+0x18f/0x20d lib/dump_stack.c:118
print_deadlock_bug kernel/locking/lockdep.c:2391 [inline]
check_deadlock kernel/locking/lockdep.c:2432 [inline]
validate_chain kernel/locking/lockdep.c:3202 [inline]
__lock_acquire.cold+0x178/0x3f8 kernel/locking/lockdep.c:4380
lock_acquire+0x1f1/0xad0 kernel/locking/lockdep.c:4959
_raw_spin_lock_nested+0x30/0x40 kernel/locking/spinlock.c:361
netif_addr_lock_nested include/linux/netdevice.h:4243 [inline]
dev_mc_unsync net/core/dev_addr_lists.c:915 [inline]
dev_mc_unsync+0xf4/0x190 net/core/dev_addr_lists.c:909
vlan_dev_stop+0x51/0x350 net/8021q/vlan_dev.c:315
__dev_close_many+0x1b3/0x2e0 net/core/dev.c:1599
dev_close_many+0x238/0x650 net/core/dev.c:1624
vlan_device_event+0x8ef/0x2010 net/8021q/vlan.c:450
notifier_call_chain+0xb5/0x200 kernel/notifier.c:83
call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:2027
call_netdevice_notifiers_extack net/core/dev.c:2039 [inline]
call_netdevice_notifiers net/core/dev.c:2053 [inline]
dev_close_many+0x30b/0x650 net/core/dev.c:1628
rollback_registered_many+0x3af/0xf60 net/core/dev.c:8945
unregister_netdevice_many.part.0+0x1a/0x2f0 net/core/dev.c:10113
unregister_netdevice_many+0x36/0x50 net/core/dev.c:10112
vlan_device_event+0x1ab5/0x2010 net/8021q/vlan.c:490
notifier_call_chain+0xb5/0x200 kernel/notifier.c:83
call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:2027
call_netdevice_notifiers_extack net/core/dev.c:2039 [inline]
call_netdevice_notifiers net/core/dev.c:2053 [inline]
rollback_registered_many+0x665/0xf60 net/core/dev.c:8968
rollback_registered net/core/dev.c:9013 [inline]
unregister_netdevice_queue+0x2dd/0x570 net/core/dev.c:10094
unregister_netdevice include/linux/netdevice.h:2754 [inline]
nsim_destroy+0x35/0x60 drivers/net/netdevsim/netdev.c:330
__nsim_dev_port_del+0x144/0x1e0 drivers/net/netdevsim/dev.c:941
nsim_dev_port_del_all drivers/net/netdevsim/dev.c:954 [inline]
nsim_dev_reload_destroy+0xff/0x1e0 drivers/net/netdevsim/dev.c:1130
nsim_dev_reload_down+0x6e/0xd0 drivers/net/netdevsim/dev.c:711
devlink_reload+0xc1/0x3a0 net/core/devlink.c:2797
devlink_nl_cmd_reload+0x386/0x880 net/core/devlink.c:2832
genl_family_rcv_msg_doit net/netlink/genetlink.c:691 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:736 [inline]
genl_rcv_msg+0x61d/0x9e0 net/netlink/genetlink.c:753
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469
genl_rcv+0x24/0x40 net/netlink/genetlink.c:764
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45ca59
Code: Bad RIP value.
RSP: 002b:00007fbbcff89c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004fdec0 RCX: 000000000045ca59
RDX: 0000000000000000 RSI: 0000000020000800 RDI: 0000000000000006
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000092d R14: 00000000004cbff2 R15: 00007fbbcff8a6d4


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 4a21185c Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=12e8e9c5100000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569

dashboard link: https://syzkaller.appspot.com/bug?extid=08e3d39f3eb8643216be
compiler: gcc (GCC) 10.1.0-syz 20200507

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11d2b1c5100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17aed775100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+08e3d3...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected

5.8.0-rc2-syzkaller #0 Not tainted
--------------------------------------------
syz-executor094/7550 is trying to acquire lock:
ffff8880a8f1e280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: netif_addr_lock_nested include/linux/netdevice.h:4243 [inline]
ffff8880a8f1e280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync net/core/dev_addr_lists.c:915 [inline]
ffff8880a8f1e280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync+0xf4/0x190 net/core/dev_addr_lists.c:909

but task is already holding lock:

ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:358 [inline]
ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: netif_addr_lock_bh include/linux/netdevice.h:4248 [inline]
ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync net/core/dev_addr_lists.c:914 [inline]
ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync+0xb0/0x190 net/core/dev_addr_lists.c:909

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&vlan_netdev_addr_lock_key/1);
lock(&vlan_netdev_addr_lock_key/1);

*** DEADLOCK ***

May be due to missing lock nesting notation

2 locks held by syz-executor094/7550:
#0: ffffffff8a7b0228 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:72 [inline]
#0: ffffffff8a7b0228 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x3f9/0xad0 net/core/rtnetlink.c:5457
#1: ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:358 [inline]
#1: ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: netif_addr_lock_bh include/linux/netdevice.h:4248 [inline]
#1: ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync net/core/dev_addr_lists.c:914 [inline]
#1: ffff8880876f4280 (&vlan_netdev_addr_lock_key/1){+...}-{2:2}, at: dev_mc_unsync+0xb0/0x190 net/core/dev_addr_lists.c:909

stack backtrace:
CPU: 0 PID: 7550 Comm: syz-executor094 Not tainted 5.8.0-rc2-syzkaller #0

rtnl_delete_link net/core/rtnetlink.c:2953 [inline]
rtnl_dellink+0x351/0xa70 net/core/rtnetlink.c:3005
rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5460
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469

netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

RIP: 0033:0x4495a9
Code: Bad RIP value.
RSP: 002b:00007f5a08ffddb8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dec68 RCX: 00000000004495a9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
RBP: 00000000006dec60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dec6c
R13: 00007ffef4bb9e0f R14: 00007f5a08ffe9c0 R15: 00000000006dec6c

[Cong Wang]

#syz test: https://github.com/congwang/linux.git net

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger crash:

Reported-and-tested-by: syzbot+08e3d3...@syzkaller.appspotmail.com

Tested on:

commit: 152c6a4d genetlink: get rid of family->attrbuf
git tree: https://github.com/congwang/linux.git net

kernel config: https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569
dashboard link: https://syzkaller.appspot.com/bug?extid=08e3d39f3eb8643216be
compiler: gcc (GCC) 10.1.0-syz 20200507

Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit be74294ffa24f5fbc0d6643842e3e095447e17a2
Author: Cong Wang <xiyou.w...@gmail.com>
Date: Fri Jun 26 18:24:22 2020 +0000

net: get rid of lockdep_set_class_and_subclass()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=110b0fc2900000
start commit: 4a21185c Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree: net

kernel config: https://syzkaller.appspot.com/x/.config?x=bf3aec367b9ab569
dashboard link: https://syzkaller.appspot.com/bug?extid=08e3d39f3eb8643216be

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11d2b1c5100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17aed775100000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: net: get rid of lockdep_set_class_and_subclass()

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

> Bisect log looks clean.

>
> #syz fix: net: get rid of lockdep_set_class_and_subclass()

Your 'fix:' command is accepted, but please keep syzkall...@googlegroups.com mailing list in CC next time. It serves as a history of what happened with each bug report. Thank you.