Message-ID: <67cb88d1.050a0220.d8275.022b.GAE@google.com>
Date: Fri, 07 Mar 2025 16:01:21 -0800
From: syzbot <syzbot+666871ad20c653deb9a6@...kaller.appspotmail.com>
To: davem@...emloft.net, edumazet@...gle.com, horms@...nel.org, 
	kuba@...nel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] possible deadlock in register_netdevice

Hello,

syzbot found the following issue on:

HEAD commit:    865eddcf0afb Merge branch 'mlx5-misc-enhancements-2025-03-..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16d8c878580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fbc61e4c6e816b7b
dashboard link: https://syzkaller.appspot.com/bug?extid=666871ad20c653deb9a6
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13896a54580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/15388530d696/disk-865eddcf.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/dfd22998e59b/vmlinux-865eddcf.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ecc6b8f2a90d/bzImage-865eddcf.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+666871ad20c653deb9a6@...kaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
6.14.0-rc5-syzkaller-01096-g865eddcf0afb #0 Not tainted
--------------------------------------------
dhcpcd/5501 is trying to acquire lock:
ffff88807e6fad28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2765 [inline]
ffff88807e6fad28 (&dev->lock){+.+.}-{4:4}, at: register_netdevice+0x12d8/0x1b70 net/core/dev.c:11008

but task is already holding lock:
ffff88807c708d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2765 [inline]
ffff88807c708d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock_ops include/linux/netdevice.h:2804 [inline]
ffff88807c708d28 (&dev->lock){+.+.}-{4:4}, at: dev_change_flags+0x120/0x270 net/core/dev_api.c:65

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

       CPU0
       ----
  lock(&dev->lock);
  lock(&dev->lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by dhcpcd/5501:
 #0: ffffffff8fed6848 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #0: ffffffff8fed6848 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x34c/0x1d80 net/ipv4/devinet.c:1121
 #1: ffff88807c708d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2765 [inline]
 #1: ffff88807c708d28 (&dev->lock){+.+.}-{4:4}, at: netdev_lock_ops include/linux/netdevice.h:2804 [inline]
 #1: ffff88807c708d28 (&dev->lock){+.+.}-{4:4}, at: dev_change_flags+0x120/0x270 net/core/dev_api.c:65

stack backtrace:
CPU: 0 UID: 0 PID: 5501 Comm: dhcpcd Not tainted 6.14.0-rc5-syzkaller-01096-g865eddcf0afb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_deadlock_bug+0x483/0x620 kernel/locking/lockdep.c:3039
 check_deadlock kernel/locking/lockdep.c:3091 [inline]
 validate_chain+0x15e2/0x5920 kernel/locking/lockdep.c:3893
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
 netdev_lock include/linux/netdevice.h:2765 [inline]
 register_netdevice+0x12d8/0x1b70 net/core/dev.c:11008
 bpq_new_device drivers/net/hamradio/bpqether.c:499 [inline]
 bpq_device_event+0x4b1/0x8d0 drivers/net/hamradio/bpqether.c:542
 notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85
 __dev_notify_flags+0x207/0x400
 netif_change_flags+0xf0/0x1a0 net/core/dev.c:9442
 dev_change_flags+0x146/0x270 net/core/dev_api.c:66
 devinet_ioctl+0xea2/0x1d80 net/ipv4/devinet.c:1200
 inet_ioctl+0x3d7/0x4f0 net/ipv4/af_inet.c:1001
 sock_do_ioctl+0x158/0x460 net/socket.c:1190
 sock_ioctl+0x626/0x8e0 net/socket.c:1309
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0cd048dd49
Code: 5c c3 48 8d 44 24 08 48 89 54 24 e0 48 89 44 24 c0 48 8d 44 24 d0 48 89 44 24 c8 b8 10 00 00 00 c7 44 24 b8 10 00 00 00 0f 05 <41> 89 c0 3d 00 f0 ff ff 76 10 48 8b 15 ae 60 0d 00 f7 d8 41 83 c8
RSP: 002b:00007ffe158efc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f0cd03bf6c0 RCX: 00007f0cd048dd49
RDX: 00007ffe158ffe68 RSI: 0000000000008914 RDI: 0000000000000018
RBP: 00007ffe15910028 R08: 00007ffe158ffe28 R09: 00007ffe158ffdd8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe158ffe68 R14: 0000000000000028 R15: 0000000000008914
 </TASK>


---
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