[syzbot] [net?] possible deadlock in __ipv6_dev_mc_inc
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syzbot
Mar 16, 2026, 6:33:27 AM (17 hours ago) Mar 16
to da...@davemloft.net, dsa...@kernel.org, edum...@google.com, ho...@kernel.org, ku...@kernel.org, linux-...@vger.kernel.org, net...@vger.kernel.org, pab...@redhat.com, syzkall...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: 80234b5ab240 Merge tag 'rproc-v7.0-fixes' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10f4cd52580000
kernel config: https://syzkaller.appspot.com/x/.config?x=976ba5a93c4add9e
dashboard link: https://syzkaller.appspot.com/bug?extid=afbcf622635e98bf40d2
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2e6b301fd0a3/disk-80234b5a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b7beeadf358c/vmlinux-80234b5a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0570bee580ee/bzImage-80234b5a.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+afbcf6...@syzkaller.appspotmail.com
netlink: 132 bytes leftover after parsing attributes in process `syz.2.4459'.
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.2.4459/20989 is trying to acquire lock:
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4493 [inline]
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4846 [inline]
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5378
but task is already holding lock:
ffff88803538d538 (&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
__ipv6_dev_mc_inc+0x53/0xbc0 net/ipv6/mcast.c:943
__ipv6_sock_mc_join+0x5b8/0x8e0 net/ipv6/mcast.c:234
do_ipv6_mcast_group_source+0x21e/0x270 net/ipv6/ipv6_sockglue.c:173
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:913
nbd_mark_nsock_dead+0xae/0x5c0 drivers/block/nbd.c:318
recv_work+0x5fb/0x8c0 drivers/block/nbd.c:1021
process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
process_scheduled_works kernel/workqueue.c:3358 [inline]
worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
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_start_device_ioctl drivers/block/nbd.c:1548 [inline]
__nbd_ioctl drivers/block/nbd.c:1623 [inline]
nbd_ioctl+0x4a6/0xd30 drivers/block/nbd.c:1663
blkdev_ioctl+0x5ad/0x6f0 block/ioctl.c:804
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl fs/ioctl.c:583 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
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)#53){++++}-{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:4493 [inline]
slab_alloc_node mm/slub.c:4846 [inline]
__kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5378
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
pndisc_constructor+0xf7/0x150 net/ipv6/ndisc.c:383
pneigh_create+0x2ae/0x4f0 net/core/neighbour.c:810
neigh_add+0x458/0x1210 net/core/neighbour.c:2088
rtnetlink_rcv_msg+0x3c9/0xe90 net/core/rtnetlink.c:6967
netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550
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
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 ***
3 locks held by syz.2.4459/20989:
#0: ffffffff90610828 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
#0: ffffffff90610828 (rtnl_mutex){+.+.}-{4:4}, at: rtnetlink_rcv_msg+0x371/0xe90 net/core/rtnetlink.c:6964
#1: ffffffff908161a0 (&tbl->phash_lock){+.+.}-{4:4}, at: pneigh_create+0x46/0x4f0 net/core/neighbour.c:792
#2: ffff88803538d538 (&idev->mc_lock){+.+.}-{4:4}, at: __ipv6_dev_mc_inc+0x53/0xbc0 net/ipv6/mcast.c:943
stack backtrace:
CPU: 0 UID: 0 PID: 20989 Comm: syz.2.4459 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
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:4493 [inline]
slab_alloc_node mm/slub.c:4846 [inline]
__kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5378
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
pndisc_constructor+0xf7/0x150 net/ipv6/ndisc.c:383
pneigh_create+0x2ae/0x4f0 net/core/neighbour.c:810
neigh_add+0x458/0x1210 net/core/neighbour.c:2088
rtnetlink_rcv_msg+0x3c9/0xe90 net/core/rtnetlink.c:6967
netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550
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
RIP: 0033:0x7f26f559c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f26f650a028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f26f5816090 RCX: 00007f26f559c799
RDX: 0000000000040094 RSI: 0000200000000100 RDI: 0000000000000005
RBP: 00007f26f5632c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f26f5816128 R14: 00007f26f5816090 R15: 00007fffe7ac39c8
</TASK>
---
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#syz undup
syzbot found the following issue on:
HEAD commit: 80234b5ab240 Merge tag 'rproc-v7.0-fixes' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10f4cd52580000
kernel config: https://syzkaller.appspot.com/x/.config?x=976ba5a93c4add9e
dashboard link: https://syzkaller.appspot.com/bug?extid=afbcf622635e98bf40d2
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2e6b301fd0a3/disk-80234b5a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b7beeadf358c/vmlinux-80234b5a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0570bee580ee/bzImage-80234b5a.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+afbcf6...@syzkaller.appspotmail.com
netlink: 132 bytes leftover after parsing attributes in process `syz.2.4459'.
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.2.4459/20989 is trying to acquire lock:
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4493 [inline]
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4846 [inline]
ffffffff8e9ab040 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5378
but task is already holding lock:
ffff88803538d538 (&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
__ipv6_dev_mc_inc+0x53/0xbc0 net/ipv6/mcast.c:943
__ipv6_sock_mc_join+0x5b8/0x8e0 net/ipv6/mcast.c:234
do_ipv6_mcast_group_source+0x21e/0x270 net/ipv6/ipv6_sockglue.c:173
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:913
nbd_mark_nsock_dead+0xae/0x5c0 drivers/block/nbd.c:318
recv_work+0x5fb/0x8c0 drivers/block/nbd.c:1021
process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
process_scheduled_works kernel/workqueue.c:3358 [inline]
worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
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_start_device_ioctl drivers/block/nbd.c:1548 [inline]
__nbd_ioctl drivers/block/nbd.c:1623 [inline]
nbd_ioctl+0x4a6/0xd30 drivers/block/nbd.c:1663
blkdev_ioctl+0x5ad/0x6f0 block/ioctl.c:804
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl fs/ioctl.c:583 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
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)#53){++++}-{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:4493 [inline]
slab_alloc_node mm/slub.c:4846 [inline]
__kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5378
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
pndisc_constructor+0xf7/0x150 net/ipv6/ndisc.c:383
pneigh_create+0x2ae/0x4f0 net/core/neighbour.c:810
neigh_add+0x458/0x1210 net/core/neighbour.c:2088
rtnetlink_rcv_msg+0x3c9/0xe90 net/core/rtnetlink.c:6967
netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550
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
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 ***
3 locks held by syz.2.4459/20989:
#0: ffffffff90610828 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
#0: ffffffff90610828 (rtnl_mutex){+.+.}-{4:4}, at: rtnetlink_rcv_msg+0x371/0xe90 net/core/rtnetlink.c:6964
#1: ffffffff908161a0 (&tbl->phash_lock){+.+.}-{4:4}, at: pneigh_create+0x46/0x4f0 net/core/neighbour.c:792
#2: ffff88803538d538 (&idev->mc_lock){+.+.}-{4:4}, at: __ipv6_dev_mc_inc+0x53/0xbc0 net/ipv6/mcast.c:943
stack backtrace:
CPU: 0 UID: 0 PID: 20989 Comm: syz.2.4459 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
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:4493 [inline]
slab_alloc_node mm/slub.c:4846 [inline]
__kmalloc_cache_noprof+0x4b/0x6f0 mm/slub.c:5378
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
pndisc_constructor+0xf7/0x150 net/ipv6/ndisc.c:383
pneigh_create+0x2ae/0x4f0 net/core/neighbour.c:810
neigh_add+0x458/0x1210 net/core/neighbour.c:2088
rtnetlink_rcv_msg+0x3c9/0xe90 net/core/rtnetlink.c:6967
netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2550
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
RIP: 0033:0x7f26f559c799
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f26f650a028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f26f5816090 RCX: 00007f26f559c799
RDX: 0000000000040094 RSI: 0000200000000100 RDI: 0000000000000005
RBP: 00007f26f5632c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f26f5816128 R14: 00007f26f5816090 R15: 00007fffe7ac39c8
</TASK>
---
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