[v5.15] possible deadlock in ax25_setsockopt

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0c935c049b5c Linux 5.15.179
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1648fe98580000
kernel config: https://syzkaller.appspot.com/x/.config?x=bcb6af887426ce59
dashboard link: https://syzkaller.appspot.com/bug?extid=e639d398eb30645338c5
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/75b060834e1e/disk-0c935c04.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d42b06ae465d/vmlinux-0c935c04.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d5217676cd35/bzImage-0c935c04.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e639d3...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.179-syzkaller #0 Not tainted
------------------------------------------------------
syz.0.25/4385 is trying to acquire lock:
ffffffff8dc43ac8 (rtnl_mutex){+.+.}-{3:3}, at: ax25_setsockopt+0xa3a/0xe70 net/ax25/af_ax25.c:676

but task is already holding lock:
ffff8880748ab120 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1684 [inline]
ffff8880748ab120 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x206/0xe70 net/ax25/af_ax25.c:570

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (sk_lock-AF_AX25){+.+.}-{0:0}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
lock_sock_nested+0x44/0x100 net/core/sock.c:3253
lock_sock include/net/sock.h:1684 [inline]
ax25_kill_by_device net/ax25/af_ax25.c:99 [inline]
ax25_device_event+0x239/0x510 net/ax25/af_ax25.c:142
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:391
call_netdevice_notifiers_extack net/core/dev.c:2061 [inline]
call_netdevice_notifiers net/core/dev.c:2075 [inline]
dev_close_many+0x32c/0x4b0 net/core/dev.c:1650
dev_close+0x1b3/0x2b0 net/core/dev.c:1672
bpq_device_event+0x3c8/0x9d0 drivers/net/hamradio/bpqether.c:548
notifier_call_chain kernel/notifier.c:83 [inline]
raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:391
call_netdevice_notifiers_extack net/core/dev.c:2061 [inline]
call_netdevice_notifiers net/core/dev.c:2075 [inline]
dev_close_many+0x32c/0x4b0 net/core/dev.c:1650
dev_close+0x1b3/0x2b0 net/core/dev.c:1672
bond_setup_by_slave+0x66/0x390 drivers/net/bonding/bond_main.c:1471
bond_enslave+0x7b1/0x3c20 drivers/net/bonding/bond_main.c:1855
bond_do_ioctl+0x2a6/0xb40 drivers/net/bonding/bond_main.c:4238
dev_ifsioc+0xd7a/0x10c0 net/core/dev_ioctl.c:417
dev_ioctl+0x504/0xf60 net/core/dev_ioctl.c:587
sock_do_ioctl+0x34f/0x5a0 net/socket.c:1154
sock_ioctl+0x484/0x770 net/socket.c:1257
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (rtnl_mutex){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
ax25_setsockopt+0xa3a/0xe70 net/ax25/af_ax25.c:676
__sys_setsockopt+0x57e/0x990 net/socket.c:2203
__do_sys_setsockopt net/socket.c:2214 [inline]
__se_sys_setsockopt net/socket.c:2211 [inline]
__x64_sys_setsockopt+0xb1/0xc0 net/socket.c:2211
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sk_lock-AF_AX25);
lock(rtnl_mutex);
lock(sk_lock-AF_AX25);
lock(rtnl_mutex);

*** DEADLOCK ***

1 lock held by syz.0.25/4385:
#0: ffff8880748ab120 (sk_lock-AF_AX25){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1684 [inline]
#0: ffff8880748ab120 (sk_lock-AF_AX25){+.+.}-{0:0}, at: ax25_setsockopt+0x206/0xe70 net/ax25/af_ax25.c:570

stack backtrace:
CPU: 1 PID: 4385 Comm: syz.0.25 Not tainted 5.15.179-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
check_noncircular+0x2f8/0x3b0 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+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
ax25_setsockopt+0xa3a/0xe70 net/ax25/af_ax25.c:676
__sys_setsockopt+0x57e/0x990 net/socket.c:2203
__do_sys_setsockopt net/socket.c:2214 [inline]
__se_sys_setsockopt net/socket.c:2211 [inline]
__x64_sys_setsockopt+0xb1/0xc0 net/socket.c:2211
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fef7b7fc169
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:00007fef79665038 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007fef7ba14fa0 RCX: 00007fef7b7fc169
RDX: 0000000000000019 RSI: 0000000000000101 RDI: 0000000000000004
RBP: 00007fef7b87d2a0 R08: 0000000000000010 R09: 0000000000000000
R10: 0000200000000340 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fef7ba14fa0 R15: 00007ffc9b7bba18
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.