[syzbot] [kernfs?] possible deadlock in kernfs_iop_setattr
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syzbot
Mar 25, 2026, 8:43:27 AM (yesterday) Mar 25
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Hello,
syzbot found the following issue on:
HEAD commit: e069034bd660 Merge branch 'net-macb-fix-two-lock-warnings-..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=13cf606a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6754c86e8d9e4c91
dashboard link: https://syzkaller.appspot.com/bug?extid=98b54002b447b9825ad0
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f16068fdd943/disk-e069034b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9e37fb157caa/vmlinux-e069034b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e29f095e41cd/bzImage-e069034b.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+98b540...@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.5991/28469 is trying to acquire lock:
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4489 [inline]
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4843 [inline]
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4873
but task is already holding lock:
ffff888035aeea20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_setattr+0x83/0x3f0 fs/kernfs/inode.c:123
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #7 (&root->kernfs_iattr_rwsem){++++}-{4:4}:
down_read+0x47/0x2e0 kernel/locking/rwsem.c:1537
kernfs_iop_permission+0x7f/0x430 fs/kernfs/inode.c:289
do_inode_permission fs/namei.c:578 [inline]
inode_permission+0x46f/0x5f0 fs/namei.c:648
cgroup_may_write kernel/cgroup/cgroup.c:5308 [inline]
cgroup_procs_write_permission kernel/cgroup/cgroup.c:5328 [inline]
cgroup_attach_permissions+0x286/0x9e0 kernel/cgroup/cgroup.c:5351
__cgroup_procs_write+0x23a/0x300 kernel/cgroup/cgroup.c:5394
cgroup_threads_write+0x24/0x50 kernel/cgroup/cgroup.c:5424
cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:4310
kernfs_fop_write_iter+0x3af/0x540 fs/kernfs/file.c:352
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x61d/0xb90 fs/read_write.c:688
ksys_write+0x150/0x270 fs/read_write.c:740
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #6 (cpu_hotplug_lock){++++}-{0:0}:
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
cpus_read_lock+0x42/0x160 kernel/cpu.c:490
static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190
nbd_reconnect_socket drivers/block/nbd.c:1342 [inline]
nbd_genl_reconfigure+0x132f/0x1ea0 drivers/block/nbd.c:2431
genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
netlink_rcv_skb+0x232/0x4b0 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+0x80f/0x9b0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2683 [inline]
__se_sys_sendmsg net/socket.c:2681 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:614 [inline]
__mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
nbd_queue_rq+0x37b/0x1100 drivers/block/nbd.c:1207
blk_mq_dispatch_rq_list+0xa70/0x1910 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+0xdcc/0x1600 block/blk-mq-sched.c:307
blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386
blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1
blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
__blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
blk_finish_plug block/blk-core.c:1257 [inline]
__submit_bio+0x28d/0x580 block/blk-core.c:649
__submit_bio_noacct_mq block/blk-core.c:722 [inline]
submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
submit_bh fs/buffer.c:2826 [inline]
block_read_full_folio+0x599/0x830 fs/buffer.c:2444
filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
do_read_cache_folio+0x358/0x590 mm/filemap.c:4101
read_mapping_folio include/linux/pagemap.h:1028 [inline]
read_part_sector+0xb6/0x2b0 block/partitions/core.c:723
adfspart_check_ICS+0xa5/0xa40 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+0x7ba/0x1550 block/partitions/core.c:694
blkdev_get_whole+0x380/0x510 block/bdev.c:764
bdev_open+0x31e/0xd30 block/bdev.c:973
blkdev_open+0x470/0x610 block/fops.c:697
do_dentry_open+0x785/0x14e0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/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+0x19f/0x1300 kernel/locking/mutex.c:776
nbd_queue_rq+0xc6/0x1100 drivers/block/nbd.c:1199
blk_mq_dispatch_rq_list+0xa70/0x1910 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+0xdcc/0x1600 block/blk-mq-sched.c:307
blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386
blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1
blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
__blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
blk_finish_plug block/blk-core.c:1257 [inline]
__submit_bio+0x28d/0x580 block/blk-core.c:649
__submit_bio_noacct_mq block/blk-core.c:722 [inline]
submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
submit_bh fs/buffer.c:2826 [inline]
block_read_full_folio+0x599/0x830 fs/buffer.c:2444
filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
do_read_cache_folio+0x358/0x590 mm/filemap.c:4101
read_mapping_folio include/linux/pagemap.h:1028 [inline]
read_part_sector+0xb6/0x2b0 block/partitions/core.c:723
adfspart_check_ICS+0xa5/0xa40 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+0x7ba/0x1550 block/partitions/core.c:694
blkdev_get_whole+0x380/0x510 block/bdev.c:764
bdev_open+0x31e/0xd30 block/bdev.c:973
blkdev_open+0x470/0x610 block/fops.c:697
do_dentry_open+0x785/0x14e0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/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+0xca/0x3e0 kernel/rcu/srcutree.c:1505
elevator_switch+0x1e8/0x7a0 block/elevator.c:576
elevator_change+0x2cc/0x450 block/elevator.c:681
elevator_set_default+0x36c/0x430 block/elevator.c:754
blk_register_queue+0x366/0x430 block/blk-sysfs.c:946
__add_disk+0x677/0xd50 block/genhd.c:528
add_disk_fwnode+0xfb/0x480 block/genhd.c:597
add_disk include/linux/blkdev.h:785 [inline]
nbd_dev_add+0x72c/0xb50 drivers/block/nbd.c:1984
nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
do_one_initcall+0x250/0x8d0 init/main.c:1382
do_initcall_level+0x104/0x190 init/main.c:1444
do_initcalls+0x59/0xa0 init/main.c:1460
kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
kernel_init+0x1d/0x1d0 init/main.c:1582
ret_from_fork+0x51e/0xb90 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+0x19f/0x1300 kernel/locking/mutex.c:776
elevator_change+0x1b3/0x450 block/elevator.c:679
elevator_set_none+0xb5/0x140 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+0x5e7/0x1a60 block/blk-mq.c:5220
nbd_start_device+0x17f/0xb10 drivers/block/nbd.c:1489
nbd_genl_connect+0x165b/0x1cf0 drivers/block/nbd.c:2239
genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
netlink_rcv_skb+0x232/0x4b0 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+0x80f/0x9b0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2683 [inline]
__se_sys_sendmsg net/socket.c:2681 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&q->q_usage_counter(io)#50){++++}-{0:0}:
blk_alloc_queue+0x546/0x680 block/blk-core.c:461
blk_mq_alloc_queue block/blk-mq.c:4429 [inline]
__blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4476
nbd_dev_add+0x499/0xb50 drivers/block/nbd.c:1954
nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
do_one_initcall+0x250/0x8d0 init/main.c:1382
do_initcall_level+0x104/0x190 init/main.c:1444
do_initcalls+0x59/0xa0 init/main.c:1460
kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
kernel_init+0x1d/0x1d0 init/main.c:1582
ret_from_fork+0x51e/0xb90 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
fs_reclaim_acquire+0x71/0x100 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]
kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4873
__kernfs_iattrs+0xdf/0x340 fs/kernfs/inode.c:36
kernfs_iattrs fs/kernfs/inode.c:61 [inline]
__kernfs_setattr fs/kernfs/inode.c:74 [inline]
kernfs_iop_setattr+0xea/0x3f0 fs/kernfs/inode.c:128
notify_change+0xc1a/0xf40 fs/attr.c:556
do_truncate+0x1c2/0x250 fs/open.c:68
handle_truncate fs/namei.c:4279 [inline]
do_open fs/namei.c:4675 [inline]
path_openat+0x2f89/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/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 --> cpu_hotplug_lock --> &root->kernfs_iattr_rwsem
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&root->kernfs_iattr_rwsem);
lock(cpu_hotplug_lock);
lock(&root->kernfs_iattr_rwsem);
lock(fs_reclaim);
*** DEADLOCK ***
3 locks held by syz.3.5991/28469:
#0: ffff88807a7ae420 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
#1: ffff88806ddf9528 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: inode_lock_killable include/linux/fs.h:1033 [inline]
#1: ffff88806ddf9528 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: do_truncate+0x18f/0x250 fs/open.c:63
#2: ffff888035aeea20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_setattr+0x83/0x3f0 fs/kernfs/inode.c:123
stack backtrace:
CPU: 1 UID: 0 PID: 28469 Comm: syz.3.5991 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
fs_reclaim_acquire+0x71/0x100 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]
kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4873
__kernfs_iattrs+0xdf/0x340 fs/kernfs/inode.c:36
kernfs_iattrs fs/kernfs/inode.c:61 [inline]
__kernfs_setattr fs/kernfs/inode.c:74 [inline]
kernfs_iop_setattr+0xea/0x3f0 fs/kernfs/inode.c:128
notify_change+0xc1a/0xf40 fs/attr.c:556
do_truncate+0x1c2/0x250 fs/open.c:68
handle_truncate fs/namei.c:4279 [inline]
do_open fs/namei.c:4675 [inline]
path_openat+0x2f89/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9a91b9c799
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:00007f9a92b1c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f9a91e15fa0 RCX: 00007f9a91b9c799
RDX: 000000000000275a RSI: 0000200000000000 RDI: 0000000000000006
RBP: 00007f9a91c32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9a91e16038 R14: 00007f9a91e15fa0 R15: 00007ffebab4e6b8
</TASK>
---
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syzbot found the following issue on:
HEAD commit: e069034bd660 Merge branch 'net-macb-fix-two-lock-warnings-..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=13cf606a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6754c86e8d9e4c91
dashboard link: https://syzkaller.appspot.com/bug?extid=98b54002b447b9825ad0
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f16068fdd943/disk-e069034b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9e37fb157caa/vmlinux-e069034b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e29f095e41cd/bzImage-e069034b.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+98b540...@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.5991/28469 is trying to acquire lock:
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4489 [inline]
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4843 [inline]
ffffffff8e883040 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4873
but task is already holding lock:
ffff888035aeea20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_setattr+0x83/0x3f0 fs/kernfs/inode.c:123
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #7 (&root->kernfs_iattr_rwsem){++++}-{4:4}:
down_read+0x47/0x2e0 kernel/locking/rwsem.c:1537
kernfs_iop_permission+0x7f/0x430 fs/kernfs/inode.c:289
do_inode_permission fs/namei.c:578 [inline]
inode_permission+0x46f/0x5f0 fs/namei.c:648
cgroup_may_write kernel/cgroup/cgroup.c:5308 [inline]
cgroup_procs_write_permission kernel/cgroup/cgroup.c:5328 [inline]
cgroup_attach_permissions+0x286/0x9e0 kernel/cgroup/cgroup.c:5351
__cgroup_procs_write+0x23a/0x300 kernel/cgroup/cgroup.c:5394
cgroup_threads_write+0x24/0x50 kernel/cgroup/cgroup.c:5424
cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:4310
kernfs_fop_write_iter+0x3af/0x540 fs/kernfs/file.c:352
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x61d/0xb90 fs/read_write.c:688
ksys_write+0x150/0x270 fs/read_write.c:740
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #6 (cpu_hotplug_lock){++++}-{0:0}:
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
cpus_read_lock+0x42/0x160 kernel/cpu.c:490
static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190
nbd_reconnect_socket drivers/block/nbd.c:1342 [inline]
nbd_genl_reconfigure+0x132f/0x1ea0 drivers/block/nbd.c:2431
genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
netlink_rcv_skb+0x232/0x4b0 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+0x80f/0x9b0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2683 [inline]
__se_sys_sendmsg net/socket.c:2681 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:614 [inline]
__mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
nbd_queue_rq+0x37b/0x1100 drivers/block/nbd.c:1207
blk_mq_dispatch_rq_list+0xa70/0x1910 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+0xdcc/0x1600 block/blk-mq-sched.c:307
blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386
blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1
blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
__blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
blk_finish_plug block/blk-core.c:1257 [inline]
__submit_bio+0x28d/0x580 block/blk-core.c:649
__submit_bio_noacct_mq block/blk-core.c:722 [inline]
submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
submit_bh fs/buffer.c:2826 [inline]
block_read_full_folio+0x599/0x830 fs/buffer.c:2444
filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
do_read_cache_folio+0x358/0x590 mm/filemap.c:4101
read_mapping_folio include/linux/pagemap.h:1028 [inline]
read_part_sector+0xb6/0x2b0 block/partitions/core.c:723
adfspart_check_ICS+0xa5/0xa40 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+0x7ba/0x1550 block/partitions/core.c:694
blkdev_get_whole+0x380/0x510 block/bdev.c:764
bdev_open+0x31e/0xd30 block/bdev.c:973
blkdev_open+0x470/0x610 block/fops.c:697
do_dentry_open+0x785/0x14e0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/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+0x19f/0x1300 kernel/locking/mutex.c:776
nbd_queue_rq+0xc6/0x1100 drivers/block/nbd.c:1199
blk_mq_dispatch_rq_list+0xa70/0x1910 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+0xdcc/0x1600 block/blk-mq-sched.c:307
blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
blk_mq_run_hw_queue+0x348/0x4f0 block/blk-mq.c:2386
blk_mq_dispatch_list+0xd16/0xe10 include/linux/spinlock.h:-1
blk_mq_flush_plug_list+0x48d/0x570 block/blk-mq.c:2997
__blk_flush_plug+0x3ed/0x4d0 block/blk-core.c:1230
blk_finish_plug block/blk-core.c:1257 [inline]
__submit_bio+0x28d/0x580 block/blk-core.c:649
__submit_bio_noacct_mq block/blk-core.c:722 [inline]
submit_bio_noacct_nocheck+0x2f4/0xa70 block/blk-core.c:753
submit_bh fs/buffer.c:2826 [inline]
block_read_full_folio+0x599/0x830 fs/buffer.c:2444
filemap_read_folio+0x137/0x3b0 mm/filemap.c:2501
do_read_cache_folio+0x358/0x590 mm/filemap.c:4101
read_mapping_folio include/linux/pagemap.h:1028 [inline]
read_part_sector+0xb6/0x2b0 block/partitions/core.c:723
adfspart_check_ICS+0xa5/0xa40 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+0x7ba/0x1550 block/partitions/core.c:694
blkdev_get_whole+0x380/0x510 block/bdev.c:764
bdev_open+0x31e/0xd30 block/bdev.c:973
blkdev_open+0x470/0x610 block/fops.c:697
do_dentry_open+0x785/0x14e0 fs/open.c:949
vfs_open+0x3b/0x340 fs/open.c:1081
do_open fs/namei.c:4671 [inline]
path_openat+0x2e08/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/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+0xca/0x3e0 kernel/rcu/srcutree.c:1505
elevator_switch+0x1e8/0x7a0 block/elevator.c:576
elevator_change+0x2cc/0x450 block/elevator.c:681
elevator_set_default+0x36c/0x430 block/elevator.c:754
blk_register_queue+0x366/0x430 block/blk-sysfs.c:946
__add_disk+0x677/0xd50 block/genhd.c:528
add_disk_fwnode+0xfb/0x480 block/genhd.c:597
add_disk include/linux/blkdev.h:785 [inline]
nbd_dev_add+0x72c/0xb50 drivers/block/nbd.c:1984
nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
do_one_initcall+0x250/0x8d0 init/main.c:1382
do_initcall_level+0x104/0x190 init/main.c:1444
do_initcalls+0x59/0xa0 init/main.c:1460
kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
kernel_init+0x1d/0x1d0 init/main.c:1582
ret_from_fork+0x51e/0xb90 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+0x19f/0x1300 kernel/locking/mutex.c:776
elevator_change+0x1b3/0x450 block/elevator.c:679
elevator_set_none+0xb5/0x140 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+0x5e7/0x1a60 block/blk-mq.c:5220
nbd_start_device+0x17f/0xb10 drivers/block/nbd.c:1489
nbd_genl_connect+0x165b/0x1cf0 drivers/block/nbd.c:2239
genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114
genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209
netlink_rcv_skb+0x232/0x4b0 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+0x80f/0x9b0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2683 [inline]
__se_sys_sendmsg net/socket.c:2681 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&q->q_usage_counter(io)#50){++++}-{0:0}:
blk_alloc_queue+0x546/0x680 block/blk-core.c:461
blk_mq_alloc_queue block/blk-mq.c:4429 [inline]
__blk_mq_alloc_disk+0x197/0x390 block/blk-mq.c:4476
nbd_dev_add+0x499/0xb50 drivers/block/nbd.c:1954
nbd_init+0x168/0x1f0 drivers/block/nbd.c:2692
do_one_initcall+0x250/0x8d0 init/main.c:1382
do_initcall_level+0x104/0x190 init/main.c:1444
do_initcalls+0x59/0xa0 init/main.c:1460
kernel_init_freeable+0x2a6/0x3e0 init/main.c:1692
kernel_init+0x1d/0x1d0 init/main.c:1582
ret_from_fork+0x51e/0xb90 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
fs_reclaim_acquire+0x71/0x100 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]
kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4873
__kernfs_iattrs+0xdf/0x340 fs/kernfs/inode.c:36
kernfs_iattrs fs/kernfs/inode.c:61 [inline]
__kernfs_setattr fs/kernfs/inode.c:74 [inline]
kernfs_iop_setattr+0xea/0x3f0 fs/kernfs/inode.c:128
notify_change+0xc1a/0xf40 fs/attr.c:556
do_truncate+0x1c2/0x250 fs/open.c:68
handle_truncate fs/namei.c:4279 [inline]
do_open fs/namei.c:4675 [inline]
path_openat+0x2f89/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/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 --> cpu_hotplug_lock --> &root->kernfs_iattr_rwsem
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&root->kernfs_iattr_rwsem);
lock(cpu_hotplug_lock);
lock(&root->kernfs_iattr_rwsem);
lock(fs_reclaim);
*** DEADLOCK ***
3 locks held by syz.3.5991/28469:
#0: ffff88807a7ae420 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493
#1: ffff88806ddf9528 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: inode_lock_killable include/linux/fs.h:1033 [inline]
#1: ffff88806ddf9528 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: do_truncate+0x18f/0x250 fs/open.c:63
#2: ffff888035aeea20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_setattr+0x83/0x3f0 fs/kernfs/inode.c:123
stack backtrace:
CPU: 1 UID: 0 PID: 28469 Comm: syz.3.5991 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4348 [inline]
fs_reclaim_acquire+0x71/0x100 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]
kmem_cache_alloc_noprof+0x40/0x650 mm/slub.c:4873
__kernfs_iattrs+0xdf/0x340 fs/kernfs/inode.c:36
kernfs_iattrs fs/kernfs/inode.c:61 [inline]
__kernfs_setattr fs/kernfs/inode.c:74 [inline]
kernfs_iop_setattr+0xea/0x3f0 fs/kernfs/inode.c:128
notify_change+0xc1a/0xf40 fs/attr.c:556
do_truncate+0x1c2/0x250 fs/open.c:68
handle_truncate fs/namei.c:4279 [inline]
do_open fs/namei.c:4675 [inline]
path_openat+0x2f89/0x3860 fs/namei.c:4830
do_file_open+0x23e/0x4a0 fs/namei.c:4859
do_sys_openat2+0x113/0x200 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+0x138/0x170 fs/open.c:1383
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9a91b9c799
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:00007f9a92b1c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f9a91e15fa0 RCX: 00007f9a91b9c799
RDX: 000000000000275a RSI: 0000200000000000 RDI: 0000000000000006
RBP: 00007f9a91c32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9a91e16038 R14: 00007f9a91e15fa0 R15: 00007ffebab4e6b8
</TASK>
---
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