====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc1-syzkaller-00101-g27605c8c0f69 #0 Not tainted ------------------------------------------------------ syz.1.2255/15935 is trying to acquire lock: ffffffff8e52ea68 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0xb4c/0x1470 mm/percpu.c:1782 but task is already holding lock: ffff888142bc27c8 (&q->q_usage_counter(io)#18){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#18){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x175/0x290 block/blk-mq.c:4396 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4443 loop_add+0x49e/0xb70 drivers/block/loop.c:2014 loop_init+0x164/0x270 drivers/block/loop.c:2249 do_one_initcall+0x120/0x6e0 init/main.c:1273 do_initcall_level init/main.c:1335 [inline] do_initcalls init/main.c:1351 [inline] do_basic_setup init/main.c:1370 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1583 kernel_init+0x1c/0x2b0 init/main.c:1473 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4045 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4059 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x162/0x610 mm/page_alloc.c:4727 __alloc_frozen_pages_noprof+0x18b/0x23f0 mm/page_alloc.c:4948 __alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:4993 __alloc_pages_node_noprof include/linux/gfp.h:284 [inline] alloc_pages_node_noprof include/linux/gfp.h:311 [inline] pcpu_alloc_pages mm/percpu-vm.c:95 [inline] pcpu_populate_chunk+0x110/0xb00 mm/percpu-vm.c:285 pcpu_alloc_noprof+0x86a/0x1470 mm/percpu.c:1870 xt_percpu_counter_alloc+0x13e/0x1b0 net/netfilter/x_tables.c:1931 find_check_entry.constprop.0+0xbc/0x9b0 net/ipv4/netfilter/ip_tables.c:526 translate_table+0xc98/0x1720 net/ipv4/netfilter/ip_tables.c:716 ipt_register_table+0x102/0x430 net/ipv4/netfilter/ip_tables.c:1742 iptable_security_table_init+0x40/0x60 net/ipv4/netfilter/iptable_security.c:46 xt_find_table_lock+0x2e1/0x520 net/netfilter/x_tables.c:1260 xt_request_find_table_lock+0x28/0xf0 net/netfilter/x_tables.c:1285 get_info+0x190/0x610 net/ipv4/netfilter/ip_tables.c:963 do_ipt_get_ctl+0x169/0xa10 net/ipv4/netfilter/ip_tables.c:1659 nf_getsockopt+0x7c/0xe0 net/netfilter/nf_sockopt.c:116 ip_getsockopt+0x18c/0x1e0 net/ipv4/ip_sockglue.c:1777 tcp_getsockopt+0x9e/0x100 net/ipv4/tcp.c:4760 do_sock_getsockopt+0x3ff/0x800 net/socket.c:2357 __sys_getsockopt+0x123/0x1b0 net/socket.c:2386 __do_sys_getsockopt net/socket.c:2393 [inline] __se_sys_getsockopt net/socket.c:2390 [inline] __x64_sys_getsockopt+0xbd/0x160 net/socket.c:2390 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (pcpu_alloc_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 pcpu_alloc_noprof+0xb4c/0x1470 mm/percpu.c:1782 blk_stat_alloc_callback+0xc8/0x280 block/blk-stat.c:116 wbt_init+0xac/0x540 block/blk-wbt.c:903 queue_wb_lat_store+0x354/0x3d0 block/blk-sysfs.c:603 queue_attr_store+0x276/0x320 block/blk-sysfs.c:805 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c4/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 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: pcpu_alloc_mutex --> fs_reclaim --> &q->q_usage_counter(io)#18 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#18); lock(fs_reclaim); lock(&q->q_usage_counter(io)#18); lock(pcpu_alloc_mutex); *** DEADLOCK *** 6 locks held by syz.1.2255/15935: #0: ffff88807846a2b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1213 #1: ffff888035fc2428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738 #2: ffff888060faa088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325 #3: ffff888025e734b8 (kn->active#108){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326 #4: ffff888142bc27c8 (&q->q_usage_counter(io)#18){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 #5: ffff888142bc2800 (&q->q_usage_counter(queue)#21){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 stack backtrace: CPU: 1 UID: 0 PID: 15935 Comm: syz.1.2255 Not tainted 6.16.0-rc1-syzkaller-00101-g27605c8c0f69 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178 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 pcpu_alloc_noprof+0xb4c/0x1470 mm/percpu.c:1782 blk_stat_alloc_callback+0xc8/0x280 block/blk-stat.c:116 wbt_init+0xac/0x540 block/blk-wbt.c:903 queue_wb_lat_store+0x354/0x3d0 block/blk-sysfs.c:603 queue_attr_store+0x276/0x320 block/blk-sysfs.c:805 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c4/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f96b3f8e929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f96b4e28038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f96b41b6160 RCX: 00007f96b3f8e929 RDX: 0000000000000009 RSI: 00002000000001c0 RDI: 0000000000000004 RBP: 00007f96b4010b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f96b41b6160 R15: 00007ffefdfe6198