On Wed, Jun 25, 2025 at 11:06 PM Stanislav Fomichev <stfomichev@xxxxxxxxx> wrote: > > On 06/25, Jason Xing wrote: > > On Wed, Jun 25, 2025 at 2:51 AM syzbot > > <syzbot+e67ea9c235b13b4f0020@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: 78f4e737a53e Merge tag 'for-6.16/dm-fixes' of git://git.ke.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=11b48f0c580000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=12ec1a20ad573841 > > > dashboard link: https://syzkaller.appspot.com/bug?extid=e67ea9c235b13b4f0020 > > > compiler: gcc (Debian 12.2.0-14) 12.2.0, 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/3ff97b2d201b/disk-78f4e737.raw.xz > > > vmlinux: https://storage.googleapis.com/syzbot-assets/1968f46c8915/vmlinux-78f4e737.xz > > > kernel image: https://storage.googleapis.com/syzbot-assets/3455e371b965/bzImage-78f4e737.xz > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+e67ea9c235b13b4f0020@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > netlink: 4 bytes leftover after parsing attributes in process `syz.1.1331'. > > > ====================================================== > > > WARNING: possible circular locking dependency detected > > > 6.16.0-rc3-syzkaller-00042-g78f4e737a53e #0 Not tainted > > > ------------------------------------------------------ > > > syz.1.1331/11144 is trying to acquire lock: > > > ffff888054b136b0 (&xs->mutex){+.+.}-{4:4}, at: xsk_notifier+0x101/0x280 net/xdp/xsk.c:1649 > > > > > > but task is already holding lock: > > > ffff888052f43d58 (&net->xdp.lock){+.+.}-{4:4}, at: xsk_notifier+0xa4/0x280 net/xdp/xsk.c:1645 > > > > > > which lock already depends on the new lock. > > > > > > > > > the existing dependency chain (in reverse order) is: > > > > > > -> #2 (&net->xdp.lock){+.+.}-{4:4}: > > > __mutex_lock_common kernel/locking/mutex.c:602 [inline] > > > __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 > > > xsk_notifier+0xa4/0x280 net/xdp/xsk.c:1645 > > > notifier_call_chain+0xbc/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] > > > unregister_netdevice_many_notify+0xf9d/0x2700 net/core/dev.c:12077 > > > unregister_netdevice_many net/core/dev.c:12140 [inline] > > > unregister_netdevice_queue+0x305/0x3f0 net/core/dev.c:11984 > > > register_netdevice+0x18f1/0x2270 net/core/dev.c:11149 > > > lapbeth_new_device drivers/net/wan/lapbether.c:420 [inline] > > > lapbeth_device_event+0x5b1/0xbe0 drivers/net/wan/lapbether.c:462 > > > notifier_call_chain+0xbc/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+0x12c/0x2e0 net/core/dev.c:9497 > > > netif_change_flags+0x108/0x160 net/core/dev.c:9526 > > > dev_change_flags+0xba/0x250 net/core/dev_api.c:68 > > > devinet_ioctl+0x11d5/0x1f50 net/ipv4/devinet.c:1200 > > > inet_ioctl+0x3a7/0x3f0 net/ipv4/af_inet.c:1001 > > > sock_do_ioctl+0x118/0x280 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 > > > > > > -> #1 (&dev_instance_lock_key#20){+.+.}-{4:4}: > > > __mutex_lock_common kernel/locking/mutex.c:602 [inline] > > > __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 > > > netdev_lock include/linux/netdevice.h:2756 [inline] > > > netdev_lock_ops include/net/netdev_lock.h:42 [inline] > > > xsk_bind+0x37c/0x1570 net/xdp/xsk.c:1189 > > > __sys_bind_socket net/socket.c:1810 [inline] > > > __sys_bind_socket net/socket.c:1802 [inline] > > > __sys_bind+0x1a7/0x260 net/socket.c:1841 > > > __do_sys_bind net/socket.c:1846 [inline] > > > __se_sys_bind net/socket.c:1844 [inline] > > > __x64_sys_bind+0x72/0xb0 net/socket.c:1844 > > > 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 (&xs->mutex){+.+.}-{4:4}: > > > 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 > > > __mutex_lock_common kernel/locking/mutex.c:602 [inline] > > > __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 > > > xsk_notifier+0x101/0x280 net/xdp/xsk.c:1649 > > > notifier_call_chain+0xbc/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] > > > unregister_netdevice_many_notify+0xf9d/0x2700 net/core/dev.c:12077 > > > rtnl_delete_link net/core/rtnetlink.c:3511 [inline] > > > rtnl_dellink+0x3cb/0xa80 net/core/rtnetlink.c:3553 > > > rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6944 > > > netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2534 > > > netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] > > > netlink_unicast+0x53d/0x7f0 net/netlink/af_netlink.c:1339 > > > netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883 > > > sock_sendmsg_nosec net/socket.c:712 [inline] > > > __sock_sendmsg net/socket.c:727 [inline] > > > ____sys_sendmsg+0xa98/0xc70 net/socket.c:2566 > > > ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620 > > > __sys_sendmsg+0x16d/0x220 net/socket.c:2652 > > > 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: > > > > > > Chain exists of: > > > &xs->mutex --> &dev_instance_lock_key#20 --> &net->xdp.lock > > > > > > Possible unsafe locking scenario: > > > > > > CPU0 CPU1 > > > ---- ---- > > > lock(&net->xdp.lock); > > > lock(&dev_instance_lock_key#20); > > > lock(&net->xdp.lock); > > > lock(&xs->mutex); > > > > I feel the above race map is not that right? > > > > My understanding is as shown below. > > CPU 0 CPU 1 > > --- --- > > unregister_netdevice_many_notify() > > xsk_bind() > > netdev_lock_ops(dev); > > > > mutex_lock(&xs->mutex); > > netdev_lock_ops(dev); > > xsk_notifier() > > mutex_lock(&net->xdp.lock); > > mutex_lock(&xs->mutex); > > > > So ABBA lock case happens, IIUC. > > Since we can't (easily) control the ordering in notifiers, looks like > we need to align xsk_bind ordering (to be instance lock -> xs->mutex). > LMK if you want to take a stab at this; otherwise I'll try to send a > fix. I'm still learning the af_xdp. Sure, I'm interested in it, just a bit worried if I'm capable of completing it. I will try then. Thanks, Jason
