[v5.15] possible deadlock in nr_rt_device_down

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 284087d4f7d5 Linux 5.15.158
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13591924980000
kernel config: https://syzkaller.appspot.com/x/.config?x=ab74f93e8454887c
dashboard link: https://syzkaller.appspot.com/bug?extid=4ddafda80b8d3805c84c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0accc7dacf9d/disk-284087d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fb6b5b110f8c/vmlinux-284087d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6763bebdbfea/Image-284087d4.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4ddafd...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.158-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/6985 is trying to acquire lock:
ffff0000dbf5ec70 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
ffff0000dbf5ec70 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:151 [inline]
ffff0000dbf5ec70 (&nr_node->node_lock){+...}-{2:2}, at: nr_rt_device_down+0x144/0x8fc net/netrom/nr_route.c:524

but task is already holding lock:
ffff800016b6ad58 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
ffff800016b6ad58 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xb4/0x8fc net/netrom/nr_route.c:522

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (nr_node_list_lock){+...}-{2:2}:
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x124/0x1c4 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:368 [inline]
nr_remove_node net/netrom/nr_route.c:299 [inline]
nr_del_node net/netrom/nr_route.c:355 [inline]
nr_rt_ioctl+0x13c4/0x1b0c net/netrom/nr_route.c:683
nr_ioctl+0x14c/0x4b0 net/netrom/af_netrom.c:1253
sock_do_ioctl+0x134/0x2dc net/socket.c:1140
sock_ioctl+0x4f0/0x8ac net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #0 (&nr_node->node_lock){+...}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x124/0x1c4 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:368 [inline]
nr_node_lock include/net/netrom.h:151 [inline]
nr_rt_device_down+0x144/0x8fc net/netrom/nr_route.c:524
nr_device_event+0x134/0x160 net/netrom/af_netrom.c:126
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391
__dev_notify_flags+0x2ac/0x534
dev_change_flags+0xc8/0x154 net/core/dev.c:8889
dev_ifsioc+0x140/0xfe4 net/core/dev_ioctl.c:324
dev_ioctl+0x4e0/0xd3c net/core/dev_ioctl.c:587
sock_do_ioctl+0x1dc/0x2dc net/socket.c:1154
sock_ioctl+0x4f0/0x8ac net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

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-executor.2/6985:
#0: ffff800016a36668 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:72
#1: ffff800016b6acf8 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
#1: ffff800016b6acf8 (nr_neigh_list_lock){+...}-{2:2}, at: nr_rt_device_down+0x38/0x8fc net/netrom/nr_route.c:519
#2: ffff800016b6ad58 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
#2: ffff800016b6ad58 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xb4/0x8fc net/netrom/nr_route.c:522

stack backtrace:
CPU: 0 PID: 6985 Comm: syz-executor.2 Not tainted 5.15.158-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call trace:
dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
dump_stack+0x1c/0x58 lib/dump_stack.c:113
print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2011
check_noncircular+0x2cc/0x378 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x32d4/0x7638 kernel/locking/lockdep.c:5012
lock_acquire+0x240/0x77c kernel/locking/lockdep.c:5623
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x124/0x1c4 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:368 [inline]
nr_node_lock include/net/netrom.h:151 [inline]
nr_rt_device_down+0x144/0x8fc net/netrom/nr_route.c:524
nr_device_event+0x134/0x160 net/netrom/af_netrom.c:126
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0xd4/0x164 kernel/notifier.c:391
__dev_notify_flags+0x2ac/0x534
dev_change_flags+0xc8/0x154 net/core/dev.c:8889
dev_ifsioc+0x140/0xfe4 net/core/dev_ioctl.c:324
dev_ioctl+0x4e0/0xd3c net/core/dev_ioctl.c:587
sock_do_ioctl+0x1dc/0x2dc net/socket.c:1154
sock_ioctl+0x4f0/0x8ac net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 284087d4f7d5 Linux 5.15.158
git tree: linux-5.15.y

console output: https://syzkaller.appspot.com/x/log.txt?x=12108d24980000

kernel config: https://syzkaller.appspot.com/x/.config?x=ab74f93e8454887c
dashboard link: https://syzkaller.appspot.com/bug?extid=4ddafda80b8d3805c84c
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137a1cf4980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=178d0cd0980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0accc7dacf9d/disk-284087d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fb6b5b110f8c/vmlinux-284087d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6763bebdbfea/Image-284087d4.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4ddafd...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.158-syzkaller #0 Not tainted
------------------------------------------------------

syz-executor135/4064 is trying to acquire lock:
ffff0000c1421e70 (&nr_node->node_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
ffff0000c1421e70 (&nr_node->node_lock){+...}-{2:2}, at: nr_node_lock include/net/netrom.h:151 [inline]
ffff0000c1421e70 (&nr_node->node_lock){+...}-{2:2}, at: nr_rt_device_down+0x144/0x8fc net/netrom/nr_route.c:524

3 locks held by syz-executor135/4064:

#0: ffff800016a36668 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:72
#1: ffff800016b6acf8 (nr_neigh_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
#1: ffff800016b6acf8 (nr_neigh_list_lock){+...}-{2:2}, at: nr_rt_device_down+0x38/0x8fc net/netrom/nr_route.c:519
#2: ffff800016b6ad58 (nr_node_list_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
#2: ffff800016b6ad58 (nr_node_list_lock){+...}-{2:2}, at: nr_rt_device_down+0xb4/0x8fc net/netrom/nr_route.c:522

stack backtrace:

CPU: 0 PID: 4064 Comm: syz-executor135 Not tainted 5.15.158-syzkaller #0

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.