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Message-ID: <685d5c00.a00a0220.2e5631.02aa.GAE@google.com>
Date: Thu, 26 Jun 2025 07:41:04 -0700
From: syzbot <syzbot+14afda08dc3484d5db82@...kaller.appspotmail.com>
To: eadavis@...com, linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [hams?] possible deadlock in nr_rt_ioctl (2)
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in nr_rt_device_down
======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc3-syzkaller-gee88bddf7f2f-dirty #0 Not tainted
------------------------------------------------------
syz.1.46/6768 is trying to acquire lock:
ffff888105e21e70 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888105e21e70 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
ffff888105e21e70 (&nr_node->node_lock){+...}-{3:3}, at: nr_rt_device_down+0x18e/0x810 net/netrom/nr_route.c:518
but task is already holding lock:
ffffffff90595058 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffffffff90595058 (nr_node_list_lock){+...}-{3:3}, at: nr_rt_device_down+0xd3/0x810 net/netrom/nr_route.c:516
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (nr_node_list_lock){+...}-{3:3}:
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
nr_del_node net/netrom/nr_route.c:347 [inline]
nr_rt_ioctl+0x210f/0x29a0 net/netrom/nr_route.c:677
nr_ioctl+0x19a/0x2e0 net/netrom/af_netrom.c:1254
sock_do_ioctl+0x115/0x280 net/socket.c:1190
sock_ioctl+0x227/0x6b0 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&nr_node->node_lock){+...}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain kernel/locking/lockdep.c:3911 [inline]
__lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
lock_acquire kernel/locking/lockdep.c:5871 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x33/0x40 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+0x18e/0x810 net/netrom/nr_route.c:518
nr_device_event+0x126/0x170 net/netrom/af_netrom.c:126
notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
call_netdevice_notifiers net/core/dev.c:2282 [inline]
__dev_notify_flags+0x1f7/0x2e0 net/core/dev.c:9499
netif_change_flags+0x108/0x160 net/core/dev.c:9526
dev_change_flags+0xba/0x250 net/core/dev_api.c:68
dev_ifsioc+0x1498/0x1f70 net/core/dev_ioctl.c:565
dev_ioctl+0x223/0x10e0 net/core/dev_ioctl.c:823
sock_do_ioctl+0x19d/0x280 net/socket.c:1204
sock_ioctl+0x227/0x6b0 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(nr_node_list_lock);
lock(&nr_node->node_lock);
lock(nr_node_list_lock);
lock(&nr_node->node_lock);
*** DEADLOCK ***
3 locks held by syz.1.46/6768:
#0: ffffffff9033f628 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
#0: ffffffff9033f628 (rtnl_mutex){+.+.}-{4:4}, at: dev_ioctl+0x212/0x10e0 net/core/dev_ioctl.c:822
#1: ffffffff90594ff8 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
#1: ffffffff90594ff8 (nr_neigh_list_lock){+...}-{3:3}, at: nr_rt_device_down+0x2c/0x810 net/netrom/nr_route.c:513
#2: ffffffff90595058 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
#2: ffffffff90595058 (nr_node_list_lock){+...}-{3:3}, at: nr_rt_device_down+0xd3/0x810 net/netrom/nr_route.c:516
stack backtrace:
CPU: 3 UID: 0 PID: 6768 Comm: syz.1.46 Not tainted 6.16.0-rc3-syzkaller-gee88bddf7f2f-dirty #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046
check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain kernel/locking/lockdep.c:3911 [inline]
__lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
lock_acquire kernel/locking/lockdep.c:5871 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x33/0x40 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+0x18e/0x810 net/netrom/nr_route.c:518
nr_device_event+0x126/0x170 net/netrom/af_netrom.c:126
notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2230
call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
call_netdevice_notifiers net/core/dev.c:2282 [inline]
__dev_notify_flags+0x1f7/0x2e0 net/core/dev.c:9499
netif_change_flags+0x108/0x160 net/core/dev.c:9526
dev_change_flags+0xba/0x250 net/core/dev_api.c:68
dev_ifsioc+0x1498/0x1f70 net/core/dev_ioctl.c:565
dev_ioctl+0x223/0x10e0 net/core/dev_ioctl.c:823
sock_do_ioctl+0x19d/0x280 net/socket.c:1204
sock_ioctl+0x227/0x6b0 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6abb785d29
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:00007f6abc617038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6abb975fa0 RCX: 00007f6abb785d29
RDX: 0000000020000000 RSI: 0000000000008914 RDI: 0000000000000006
RBP: 00007f6abb801b08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6abb975fa0 R15: 00007ffc3bc2e9c8
</TASK>
Tested on:
commit: ee88bddf Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1007b182580000
kernel config: https://syzkaller.appspot.com/x/.config?x=644a0493ff5118b1
dashboard link: https://syzkaller.appspot.com/bug?extid=14afda08dc3484d5db82
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch: https://syzkaller.appspot.com/x/patch.diff?x=14217dd4580000
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