syzbot


possible deadlock in __ipv6_dev_mc_inc

Status: upstream: reported on 2026/03/16 10:33
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+afbcf622635e98bf40d2@syzkaller.appspotmail.com
First crash: 9d21h, last: 3h57m
Discussions (2)
Title Replies (including bot) Last reply
[PATCH net v1] net/ipv6: mcast: fix circular locking dependency in __ipv6_dev_mc_inc() 8 (8) 2026/03/19 15:36
[syzbot] [net?] possible deadlock in __ipv6_dev_mc_inc 0 (1) 2026/03/16 10:33

Sample crash report:
hsr_slave_1: entered promiscuous mode
debugfs: 'hsr0' already exists in 'hsr'
Cannot create hsr debugfs directory
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz-executor/10048 is trying to acquire lock:
ffffffff8e9ab380 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8e9ab380 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4489 [inline]
ffffffff8e9ab380 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4843 [inline]
ffffffff8e9ab380 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5375

but task is already holding lock:
ffff88807986c538 (&idev->mc_lock){+.+.}-{4:4}, at: __ipv6_dev_mc_inc+0x53/0xbc0 net/ipv6/mcast.c:943

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #7 (&idev->mc_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       ip6_mc_source+0x1d1/0x1610 net/ipv6/mcast.c:376
       do_ipv6_mcast_group_source+0x196/0x270 net/ipv6/ipv6_sockglue.c:185
       do_ipv6_setsockopt+0x1fe3/0x4510 net/ipv6/ipv6_sockglue.c:919
       ipv6_setsockopt+0xcb/0x170 net/ipv6/ipv6_sockglue.c:973
       udpv6_setsockopt+0x7d/0xd0 net/ipv6/udp.c:1846
       do_sock_setsockopt+0xf3/0x1d0 net/socket.c:2322
       __sys_setsockopt+0x195/0x220 net/socket.c:2347
       __do_sys_setsockopt net/socket.c:2353 [inline]
       __se_sys_setsockopt net/socket.c:2350 [inline]
       __x64_sys_setsockopt+0xbd/0x160 net/socket.c:2350
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_sock_nested+0x41/0xf0 net/core/sock.c:3780
       lock_sock include/net/sock.h:1709 [inline]
       inet_shutdown+0x67/0x410 net/ipv4/af_inet.c:919
       nbd_mark_nsock_dead+0xae/0x5c0 drivers/block/nbd.c:318
       recv_work+0x5fb/0x8c0 drivers/block/nbd.c:1021
       process_one_work+0xa23/0x19a0 kernel/workqueue.c:3276
       process_scheduled_works kernel/workqueue.c:3359 [inline]
       worker_thread+0x5ef/0xe50 kernel/workqueue.c:3440
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
       nbd_queue_rq+0x428/0x1080 drivers/block/nbd.c:1207
       blk_mq_dispatch_rq_list+0x422/0x1e70 block/blk-mq.c:2148
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xcea/0x1620 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x1c0 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x23c/0x670 block/blk-mq.c:2386
       blk_mq_dispatch_list+0x51d/0x1360 block/blk-mq.c:2949
       blk_mq_flush_plug_list block/blk-mq.c:2997 [inline]
       blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2969
       __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x584/0x6c0 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x562/0xc10 block/blk-core.c:753
       submit_bio_noacct+0xd17/0x2010 block/blk-core.c:884
       blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline]
       submit_bh_wbc+0x59c/0x770 fs/buffer.c:2821
       submit_bh fs/buffer.c:2826 [inline]
       block_read_full_folio+0x264/0x8e0 fs/buffer.c:2444
       filemap_read_folio+0xfc/0x3b0 mm/filemap.c:2501
       do_read_cache_folio+0x2d7/0x6b0 mm/filemap.c:4101
       read_mapping_folio include/linux/pagemap.h:1028 [inline]
       read_part_sector+0xd1/0x370 block/partitions/core.c:723
       adfspart_check_ICS+0x93/0x910 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:142 [inline]
       blk_add_partitions block/partitions/core.c:590 [inline]
       bdev_disk_changed+0x7f8/0xc80 block/partitions/core.c:694
       blkdev_get_whole+0x187/0x290 block/bdev.c:764
       bdev_open+0x2c7/0xe40 block/bdev.c:973
       blkdev_open+0x34e/0x4f0 block/fops.c:697
       do_dentry_open+0x6d8/0x1660 fs/open.c:949
       vfs_open+0x82/0x3f0 fs/open.c:1081
       do_open fs/namei.c:4671 [inline]
       path_openat+0x208c/0x31a0 fs/namei.c:4830
       do_file_open+0x20e/0x430 fs/namei.c:4859
       do_sys_openat2+0x10d/0x1e0 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x12d/0x210 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       nbd_queue_rq+0xba/0x1080 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0x422/0x1e70 block/blk-mq.c:2148
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xcea/0x1620 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x1c0 block/blk-mq-sched.c:329
       blk_mq_run_hw_queue+0x23c/0x670 block/blk-mq.c:2386
       blk_mq_dispatch_list+0x51d/0x1360 block/blk-mq.c:2949
       blk_mq_flush_plug_list block/blk-mq.c:2997 [inline]
       blk_mq_flush_plug_list+0x130/0x600 block/blk-mq.c:2969
       __blk_flush_plug+0x2c4/0x4b0 block/blk-core.c:1230
       blk_finish_plug block/blk-core.c:1257 [inline]
       __submit_bio+0x584/0x6c0 block/blk-core.c:649
       __submit_bio_noacct_mq block/blk-core.c:722 [inline]
       submit_bio_noacct_nocheck+0x562/0xc10 block/blk-core.c:753
       submit_bio_noacct+0xd17/0x2010 block/blk-core.c:884
       blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline]
       submit_bh_wbc+0x59c/0x770 fs/buffer.c:2821
       submit_bh fs/buffer.c:2826 [inline]
       block_read_full_folio+0x264/0x8e0 fs/buffer.c:2444
       filemap_read_folio+0xfc/0x3b0 mm/filemap.c:2501
       do_read_cache_folio+0x2d7/0x6b0 mm/filemap.c:4101
       read_mapping_folio include/linux/pagemap.h:1028 [inline]
       read_part_sector+0xd1/0x370 block/partitions/core.c:723
       adfspart_check_ICS+0x93/0x910 block/partitions/acorn.c:360
       check_partition block/partitions/core.c:142 [inline]
       blk_add_partitions block/partitions/core.c:590 [inline]
       bdev_disk_changed+0x7f8/0xc80 block/partitions/core.c:694
       blkdev_get_whole+0x187/0x290 block/bdev.c:764
       bdev_open+0x2c7/0xe40 block/bdev.c:973
       blkdev_open+0x34e/0x4f0 block/fops.c:697
       do_dentry_open+0x6d8/0x1660 fs/open.c:949
       vfs_open+0x82/0x3f0 fs/open.c:1081
       do_open fs/namei.c:4671 [inline]
       path_openat+0x208c/0x31a0 fs/namei.c:4830
       do_file_open+0x20e/0x430 fs/namei.c:4859
       do_sys_openat2+0x10d/0x1e0 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x12d/0x210 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (set->srcu){.+.+}-{0:0}:
       srcu_lock_sync include/linux/srcu.h:199 [inline]
       __synchronize_srcu+0xa1/0x2a0 kernel/rcu/srcutree.c:1505
       blk_mq_wait_quiesce_done block/blk-mq.c:284 [inline]
       blk_mq_wait_quiesce_done block/blk-mq.c:281 [inline]
       blk_mq_quiesce_queue block/blk-mq.c:304 [inline]
       blk_mq_quiesce_queue+0x149/0x1c0 block/blk-mq.c:299
       elevator_switch+0x17b/0x7e0 block/elevator.c:576
       elevator_change+0x352/0x530 block/elevator.c:681
       elevator_set_default+0x29e/0x360 block/elevator.c:754
       blk_register_queue+0x412/0x590 block/blk-sysfs.c:946
       __add_disk+0x73f/0xe40 block/genhd.c:528
       add_disk_fwnode+0x118/0x5c0 block/genhd.c:597
       add_disk include/linux/blkdev.h:785 [inline]
       nbd_dev_add+0x77a/0xb10 drivers/block/nbd.c:1984
       nbd_init+0x291/0x2b0 drivers/block/nbd.c:2692
       do_one_initcall+0x11d/0x760 init/main.c:1382
       do_initcall_level init/main.c:1444 [inline]
       do_initcalls init/main.c:1460 [inline]
       do_basic_setup init/main.c:1479 [inline]
       kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692
       kernel_init+0x1f/0x1e0 init/main.c:1582
       ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       elevator_change+0x1bc/0x530 block/elevator.c:679
       elevator_set_none+0x92/0xf0 block/elevator.c:769
       blk_mq_elv_switch_none block/blk-mq.c:5110 [inline]
       __blk_mq_update_nr_hw_queues block/blk-mq.c:5155 [inline]
       blk_mq_update_nr_hw_queues+0x4c1/0x15f0 block/blk-mq.c:5220
       nbd_start_device+0x1a6/0xbd0 drivers/block/nbd.c:1489
       nbd_genl_connect+0xff2/0x1a40 drivers/block/nbd.c:2239
       genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
       netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344
       netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894
       sock_sendmsg_nosec net/socket.c:727 [inline]
       __sock_sendmsg net/socket.c:742 [inline]
       ____sys_sendmsg+0x9e1/0xb70 net/socket.c:2592
       ___sys_sendmsg+0x190/0x1e0 net/socket.c:2646
       __sys_sendmsg+0x170/0x220 net/socket.c:2678
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       blk_alloc_queue+0x610/0x790 block/blk-core.c:461
       blk_mq_alloc_queue+0x174/0x290 block/blk-mq.c:4429
       __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4476
       nbd_dev_add+0x492/0xb10 drivers/block/nbd.c:1954
       nbd_init+0x291/0x2b0 drivers/block/nbd.c:2692
       do_one_initcall+0x11d/0x760 init/main.c:1382
       do_initcall_level init/main.c:1444 [inline]
       do_initcalls init/main.c:1460 [inline]
       do_basic_setup init/main.c:1479 [inline]
       kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692
       kernel_init+0x1f/0x1e0 init/main.c:1582
       ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (fs_reclaim){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
       __fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
       fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4362
       might_alloc include/linux/sched/mm.h:317 [inline]
       slab_pre_alloc_hook mm/slub.c:4489 [inline]
       slab_alloc_node mm/slub.c:4843 [inline]
       __kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5375
       kmalloc_noprof include/linux/slab.h:950 [inline]
       kzalloc_noprof include/linux/slab.h:1188 [inline]
       mca_alloc net/ipv6/mcast.c:871 [inline]
       __ipv6_dev_mc_inc+0x2f1/0xbc0 net/ipv6/mcast.c:961
       ipv6_add_dev+0xb78/0x1520 net/ipv6/addrconf.c:471
       addrconf_notify+0x563/0x19c0 net/ipv6/addrconf.c:3654
       notifier_call_chain+0x99/0x420 kernel/notifier.c:85
       call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2249
       call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
       call_netdevice_notifiers net/core/dev.c:2301 [inline]
       register_netdevice+0x16e6/0x2210 net/core/dev.c:11462
       nsim_init_netdevsim drivers/net/netdevsim/netdev.c:1066 [inline]
       nsim_create+0xc27/0x1370 drivers/net/netdevsim/netdev.c:1148
       __nsim_dev_port_add+0x2f4/0x790 drivers/net/netdevsim/dev.c:1493
       nsim_dev_port_add_all drivers/net/netdevsim/dev.c:1549 [inline]
       nsim_drv_probe+0xeb7/0x14b0 drivers/net/netdevsim/dev.c:1710
       call_driver_probe drivers/base/dd.c:583 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:661
       __driver_probe_device+0x1de/0x400 drivers/base/dd.c:803
       driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:833
       __device_attach_driver+0x1df/0x340 drivers/base/dd.c:961
       bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
       __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1033
       device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1088
       bus_probe_device+0x64/0x160 drivers/base/bus.c:574
       device_add+0x11d9/0x1950 drivers/base/core.c:3689
       nsim_bus_dev_new drivers/net/netdevsim/bus.c:471 [inline]
       new_device_store+0x40b/0x700 drivers/net/netdevsim/bus.c:191
       bus_attr_store+0x74/0xb0 drivers/base/bus.c:172
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142
       kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:352
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x6ac/0x1070 fs/read_write.c:688
       ksys_write+0x12a/0x250 fs/read_write.c:740
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 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:
  fs_reclaim --> sk_lock-AF_INET6 --> &idev->mc_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&idev->mc_lock);
                               lock(sk_lock-AF_INET6);
                               lock(&idev->mc_lock);
  lock(fs_reclaim);

 *** DEADLOCK ***

9 locks held by syz-executor/10048:
 #0: ffff888037048420 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:740
 #1: ffff8880578e4488 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x2c2/0x5f0 fs/kernfs/file.c:343
 #2: ffff8880203f90f8 (kn->active#53){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff8880203f90f8 (kn->active#53){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x332/0x5f0 fs/kernfs/file.c:344
 #3: ffffffff8fb6a648 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: new_device_store+0xfe/0x700 drivers/net/netdevsim/bus.c:184
 #4: ffff8880475630e8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:895 [inline]
 #4: ffff8880475630e8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x7e/0x4d0 drivers/base/dd.c:1008
 #5: ffff888047562250 (&devlink->lock_key#6){+.+.}-{4:4}, at: nsim_drv_probe+0xd4/0x14b0 drivers/net/netdevsim/dev.c:1637
 #6: ffffffff90611d28 (rtnl_mutex){+.+.}-{4:4}, at: nsim_init_netdevsim drivers/net/netdevsim/netdev.c:1054 [inline]
 #6: ffffffff90611d28 (rtnl_mutex){+.+.}-{4:4}, at: nsim_create+0x936/0x1370 drivers/net/netdevsim/netdev.c:1148
 #7: ffff888047604d40 (&dev_instance_lock_key#24){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2785 [inline]
 #7: ffff888047604d40 (&dev_instance_lock_key#24){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 #7: ffff888047604d40 (&dev_instance_lock_key#24){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:39 [inline]
 #7: ffff888047604d40 (&dev_instance_lock_key#24){+.+.}-{4:4}, at: register_netdevice+0x16c6/0x2210 net/core/dev.c:11461
 #8: ffff88807986c538 (&idev->mc_lock){+.+.}-{4:4}, at: __ipv6_dev_mc_inc+0x53/0xbc0 net/ipv6/mcast.c:943

stack backtrace:
CPU: 1 UID: 0 PID: 10048 Comm: syz-executor Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
 __fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
 fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4362
 might_alloc include/linux/sched/mm.h:317 [inline]
 slab_pre_alloc_hook mm/slub.c:4489 [inline]
 slab_alloc_node mm/slub.c:4843 [inline]
 __kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5375
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 mca_alloc net/ipv6/mcast.c:871 [inline]
 __ipv6_dev_mc_inc+0x2f1/0xbc0 net/ipv6/mcast.c:961
 ipv6_add_dev+0xb78/0x1520 net/ipv6/addrconf.c:471
 addrconf_notify+0x563/0x19c0 net/ipv6/addrconf.c:3654
 notifier_call_chain+0x99/0x420 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2249
 call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
 call_netdevice_notifiers net/core/dev.c:2301 [inline]
 register_netdevice+0x16e6/0x2210 net/core/dev.c:11462
 nsim_init_netdevsim drivers/net/netdevsim/netdev.c:1066 [inline]
 nsim_create+0xc27/0x1370 drivers/net/netdevsim/netdev.c:1148
 __nsim_dev_port_add+0x2f4/0x790 drivers/net/netdevsim/dev.c:1493
 nsim_dev_port_add_all drivers/net/netdevsim/dev.c:1549 [inline]
 nsim_drv_probe+0xeb7/0x14b0 drivers/net/netdevsim/dev.c:1710
 call_driver_probe drivers/base/dd.c:583 [inline]
 really_probe+0x241/0xa60 drivers/base/dd.c:661
 __driver_probe_device+0x1de/0x400 drivers/base/dd.c:803
 driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:833
 __device_attach_driver+0x1df/0x340 drivers/base/dd.c:961
 bus_for_each_drv+0x159/0x1e0 drivers/base/bus.c:500
 __device_attach+0x1e4/0x4d0 drivers/base/dd.c:1033
 device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1088
 bus_probe_device+0x64/0x160 drivers/base/bus.c:574
 device_add+0x11d9/0x1950 drivers/base/core.c:3689
 nsim_bus_dev_new drivers/net/netdevsim/bus.c:471 [inline]
 new_device_store+0x40b/0x700 drivers/net/netdevsim/bus.c:191
 bus_attr_store+0x74/0xb0 drivers/base/bus.c:172
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5b3d75cfce
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007ffd461ee8f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000555577178500 RCX: 00007f5b3d75cfce
RDX: 0000000000000003 RSI: 00007ffd461ee980 RDI: 0000000000000005
RBP: 00007f5b3d833540 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ffd461ee980 R14: 00007f5b3e544620 R15: 0000000000000003
 </TASK>

Crashes (27):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/22 00:16 upstream 113ae7b4decc 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root possible deadlock in __ipv6_dev_mc_inc
2026/03/12 10:29 upstream 80234b5ab240 4efadf07 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root possible deadlock in __ipv6_dev_mc_inc
2026/03/22 02:31 upstream a0c83177734a 5b92003d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in __ipv6_dev_mc_inc
2026/03/17 12:59 upstream 2d1373e4246d c01bca74 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in __ipv6_dev_mc_inc
2026/03/17 00:57 upstream 2d1373e4246d 0737c18f .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in __ipv6_dev_mc_inc
2026/03/16 12:24 upstream f338e7738378 64e21424 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in __ipv6_dev_mc_inc
2026/03/14 12:02 upstream 1c9982b49613 ee8d34d6 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in __ipv6_dev_mc_inc
2026/03/13 23:40 upstream b36eb6e3f5d8 351cb5cf .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in __ipv6_dev_mc_inc
2026/03/13 06:20 upstream 0257f64bdac7 2f7f359d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream possible deadlock in __ipv6_dev_mc_inc
2026/03/22 04:21 net bc0151c59e63 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/22 01:36 net bc0151c59e63 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/21 22:14 net bc0151c59e63 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/21 03:30 net e069034bd660 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/19 13:48 net 55dc632ab2ac bd6dcb30 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/18 19:45 net 64dcbde7f8f8 0199f9a1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/17 20:06 net 66360460cab6 c01bca74 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/16 16:10 net 43d222fbcdff 64e21424 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/22 02:42 net-next fb78a629b4f0 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/21 08:27 net-next 64cf4b95de07 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/21 06:24 net-next 64cf4b95de07 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/20 17:43 net-next ca7e99335aea 2f245add .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/18 13:27 net-next 70729af783af 0199f9a1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/17 20:14 net-next cc6421acd97f c01bca74 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/17 09:12 net-next cc6421acd97f c01bca74 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/21 23:53 linux-next 785f0eb2f85d 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/21 18:33 linux-next 785f0eb2f85d 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in __ipv6_dev_mc_inc
2026/03/21 16:19 linux-next 785f0eb2f85d 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in __ipv6_dev_mc_inc
* Struck through repros no longer work on HEAD.