[v6.1] possible deadlock in nr_del_node

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syzbot

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Jan 1, 2025, 1:38:29 AM1/1/25
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Hello,

syzbot found the following issue on:

HEAD commit: 563edd786f0a Linux 6.1.122
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14e95af8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b70d05b26edc7515
dashboard link: https://syzkaller.appspot.com/bug?extid=a40df9ec3276d68c5875
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9f111015ce9f/disk-563edd78.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/821c260b7642/vmlinux-563edd78.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9fba8f114c58/bzImage-563edd78.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a40df9...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.122-syzkaller #0 Tainted: G W
------------------------------------------------------
syz.2.20/4416 is trying to acquire lock:
ffffffff8e653178 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffffffff8e653178 (nr_neigh_list_lock){+...}-{2:2}, at: nr_remove_neigh net/netrom/nr_route.c:307 [inline]
ffffffff8e653178 (nr_neigh_list_lock){+...}-{2:2}, at: nr_del_node+0x365/0x6a0 net/netrom/nr_route.c:342

but task is already holding lock:
ffff888019ad5270 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888019ad5270 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:152 [inline]
ffff888019ad5270 (&nr_node->node_lock){+...}-{2:2}, at: nr_del_node+0xbc/0x6a0 net/netrom/nr_route.c:335

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&nr_node->node_lock){+...}-{2:2}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
nr_node_lock include/net/netrom.h:152 [inline]
nr_rt_device_down+0x155/0x7b0 net/netrom/nr_route.c:519
nr_device_event+0x12b/0x140 net/netrom/af_netrom.c:126
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:1970 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2008 [inline]
call_netdevice_notifiers net/core/dev.c:2022 [inline]
dev_close_many+0x37c/0x530 net/core/dev.c:1570
dev_close+0x1b3/0x2b0 net/core/dev.c:1592
bpq_device_event+0x35f/0x8a0 drivers/net/hamradio/bpqether.c:547
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:1970 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2008 [inline]
call_netdevice_notifiers net/core/dev.c:2022 [inline]
dev_close_many+0x37c/0x530 net/core/dev.c:1570
dev_close+0x1b3/0x2b0 net/core/dev.c:1592
bond_setup_by_slave+0x66/0x390 drivers/net/bonding/bond_main.c:1541
bond_enslave+0x7b4/0x3ad0 drivers/net/bonding/bond_main.c:1925
bond_do_ioctl+0x2a1/0xaf0 drivers/net/bonding/bond_main.c:4593
dev_ifsioc+0xe2b/0x1160 net/core/dev_ioctl.c:420
dev_ioctl+0x508/0xf70 net/core/dev_ioctl.c:588
sock_do_ioctl+0x26b/0x450 net/socket.c:1218
sock_ioctl+0x47f/0x770 net/socket.c:1321
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (nr_node_list_lock){+...}-{2:2}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
nr_rt_device_down+0xb1/0x7b0 net/netrom/nr_route.c:517
nr_device_event+0x12b/0x140 net/netrom/af_netrom.c:126
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:1970 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2008 [inline]
call_netdevice_notifiers net/core/dev.c:2022 [inline]
dev_close_many+0x37c/0x530 net/core/dev.c:1570
dev_close+0x1b3/0x2b0 net/core/dev.c:1592
bpq_device_event+0x35f/0x8a0 drivers/net/hamradio/bpqether.c:547
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:1970 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2008 [inline]
call_netdevice_notifiers net/core/dev.c:2022 [inline]
dev_close_many+0x37c/0x530 net/core/dev.c:1570
dev_close+0x1b3/0x2b0 net/core/dev.c:1592
bond_setup_by_slave+0x66/0x390 drivers/net/bonding/bond_main.c:1541
bond_enslave+0x7b4/0x3ad0 drivers/net/bonding/bond_main.c:1925
bond_do_ioctl+0x2a1/0xaf0 drivers/net/bonding/bond_main.c:4593
dev_ifsioc+0xe2b/0x1160 net/core/dev_ioctl.c:420
dev_ioctl+0x508/0xf70 net/core/dev_ioctl.c:588
sock_do_ioctl+0x26b/0x450 net/socket.c:1218
sock_ioctl+0x47f/0x770 net/socket.c:1321
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (nr_neigh_list_lock){+...}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
nr_remove_neigh net/netrom/nr_route.c:307 [inline]
nr_del_node+0x365/0x6a0 net/netrom/nr_route.c:342
nr_rt_ioctl+0x9f6/0xfb0 net/netrom/nr_route.c:678
sock_do_ioctl+0x152/0x450 net/socket.c:1204
sock_ioctl+0x47f/0x770 net/socket.c:1321
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
nr_neigh_list_lock --> nr_node_list_lock --> &nr_node->node_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&nr_node->node_lock);
lock(nr_node_list_lock);
lock(&nr_node->node_lock);
lock(nr_neigh_list_lock);

*** DEADLOCK ***

2 locks held by syz.2.20/4416:
#0: ffffffff8e6531d8 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
#0: ffffffff8e6531d8 (nr_node_list_lock){+...}-{2:2}, at: nr_del_node+0x53/0x6a0 net/netrom/nr_route.c:334
#1: ffff888019ad5270 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
#1: ffff888019ad5270 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:152 [inline]
#1: ffff888019ad5270 (&nr_node->node_lock){+...}-{2:2}, at: nr_del_node+0xbc/0x6a0 net/netrom/nr_route.c:335

stack backtrace:
CPU: 1 PID: 4416 Comm: syz.2.20 Tainted: G W 6.1.122-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
nr_remove_neigh net/netrom/nr_route.c:307 [inline]
nr_del_node+0x365/0x6a0 net/netrom/nr_route.c:342
nr_rt_ioctl+0x9f6/0xfb0 net/netrom/nr_route.c:678
sock_do_ioctl+0x152/0x450 net/socket.c:1204
sock_ioctl+0x47f/0x770 net/socket.c:1321
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff663f85d29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff664d43038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff664175fa0 RCX: 00007ff663f85d29
RDX: 0000000020000680 RSI: 000000000000890c RDI: 0000000000000008
RBP: 00007ff664001b08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ff664175fa0 R15: 00007ffdeae92b58
</TASK>


---
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syzbot

unread,
May 11, 2025, 9:18:14 PM5/11/25
to syzkaller...@googlegroups.com
Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.
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