Extracting prog: 1m51.022996648s
Minimizing prog: 5m56.67715262s
Simplifying prog options: 4m5.48698844s
Extracting C: 1m12.393152688s
Simplifying C: 0s


extracting reproducer from 3 programs
first checking the prog from the crash report
single: executing 1 programs separately with timeout 30s
testing program (duration=30s, {Threaded:true Repeat:true RepeatTimes:0 Procs:4 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal-write$auto
detailed listing:
executing program 0:
r0 = openat$auto_kernfs_file_fops_kernfs_internal(0xffffffffffffff9c, &(0x7f0000000040)='/sys/devices/virtual/block/nbd9/queue/wbt_lat_usec\x00', 0x102e82, 0x0)
write$auto(r0, &(0x7f0000000240)='0\x00\xa6\xcc\r\x91QU\x9dI\xda\x1b\xad\xb1\x9e\xc8Tt\xa8\x94\x9c\x8a\xe2\xc7cOM\xb6\xa3,!o\x9e\xb0\xadT\xfbR\xa1Y\x94V[8\x04c\xdf:]\xd9\x94\xf8F\xbb\xa2\xbb>\xade\x18\xbd\xe2\x1c\x89OO]e[\xbb\xf9\xcd\xc0\xc9\x00\xda\xac\xdd\x1a\xdd\xdd\xb9o\x1a\xab\xd5\xef\xc0\x04z\xd0I>\x8f\x00\xe5\x1c*\xed`\xfd\x15\x88\x0f\x9a\xd5\xa7\x14\f};\xabt\xd1ak\xe5\x98\xea\xe3}\x10\xab\f_\x19\x9b\x11\xb25VUK\x93\xcdd\x17\xe4\xcbA\xa5[\b\xb8;\x02tcf\x06\xfbD\x91\xcaG\xdaa:k[r\x06\xeb\xf0\x03\x00\x00\x00\x00\x00\x00\x00\xdeK\xa5\x8e\xd6\x8f\xd0UV\x11\xcb\xdd\x81\xbe\xdeL/\x06\xd5Y\a\xc1\xe9(\x95\xdfH\xf4\v\xf3C', 0x801)

program crashed: possible deadlock in pcpu_alloc_noprof
single: successfully extracted reproducer
found reproducer with 2 syscalls
minimizing guilty program
testing program (duration=45.396263044s, {Threaded:true Repeat:true RepeatTimes:0 Procs:4 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal
detailed listing:
executing program 0:
openat$auto_kernfs_file_fops_kernfs_internal(0xffffffffffffff9c, &(0x7f0000000040)='/sys/devices/virtual/block/nbd9/queue/wbt_lat_usec\x00', 0x102e82, 0x0)

program did not crash
testing program (duration=45.396263044s, {Threaded:true Repeat:true RepeatTimes:0 Procs:4 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): write$auto
detailed listing:
executing program 0:
write$auto(0xffffffffffffffff, &(0x7f0000000240)='0\x00\xa6\xcc\r\x91QU\x9dI\xda\x1b\xad\xb1\x9e\xc8Tt\xa8\x94\x9c\x8a\xe2\xc7cOM\xb6\xa3,!o\x9e\xb0\xadT\xfbR\xa1Y\x94V[8\x04c\xdf:]\xd9\x94\xf8F\xbb\xa2\xbb>\xade\x18\xbd\xe2\x1c\x89OO]e[\xbb\xf9\xcd\xc0\xc9\x00\xda\xac\xdd\x1a\xdd\xdd\xb9o\x1a\xab\xd5\xef\xc0\x04z\xd0I>\x8f\x00\xe5\x1c*\xed`\xfd\x15\x88\x0f\x9a\xd5\xa7\x14\f};\xabt\xd1ak\xe5\x98\xea\xe3}\x10\xab\f_\x19\x9b\x11\xb25VUK\x93\xcdd\x17\xe4\xcbA\xa5[\b\xb8;\x02tcf\x06\xfbD\x91\xcaG\xdaa:k[r\x06\xeb\xf0\x03\x00\x00\x00\x00\x00\x00\x00\xdeK\xa5\x8e\xd6\x8f\xd0UV\x11\xcb\xdd\x81\xbe\xdeL/\x06\xd5Y\a\xc1\xe9(\x95\xdfH\xf4\v\xf3C', 0x801)

program did not crash
testing program (duration=45.396263044s, {Threaded:true Repeat:true RepeatTimes:0 Procs:4 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal-write$auto
detailed listing:
executing program 0:
r0 = openat$auto_kernfs_file_fops_kernfs_internal(0xffffffffffffff9c, 0x0, 0x102e82, 0x0)
write$auto(r0, &(0x7f0000000240)='0\x00\xa6\xcc\r\x91QU\x9dI\xda\x1b\xad\xb1\x9e\xc8Tt\xa8\x94\x9c\x8a\xe2\xc7cOM\xb6\xa3,!o\x9e\xb0\xadT\xfbR\xa1Y\x94V[8\x04c\xdf:]\xd9\x94\xf8F\xbb\xa2\xbb>\xade\x18\xbd\xe2\x1c\x89OO]e[\xbb\xf9\xcd\xc0\xc9\x00\xda\xac\xdd\x1a\xdd\xdd\xb9o\x1a\xab\xd5\xef\xc0\x04z\xd0I>\x8f\x00\xe5\x1c*\xed`\xfd\x15\x88\x0f\x9a\xd5\xa7\x14\f};\xabt\xd1ak\xe5\x98\xea\xe3}\x10\xab\f_\x19\x9b\x11\xb25VUK\x93\xcdd\x17\xe4\xcbA\xa5[\b\xb8;\x02tcf\x06\xfbD\x91\xcaG\xdaa:k[r\x06\xeb\xf0\x03\x00\x00\x00\x00\x00\x00\x00\xdeK\xa5\x8e\xd6\x8f\xd0UV\x11\xcb\xdd\x81\xbe\xdeL/\x06\xd5Y\a\xc1\xe9(\x95\xdfH\xf4\v\xf3C', 0x801)

program did not crash
testing program (duration=45.396263044s, {Threaded:true Repeat:true RepeatTimes:0 Procs:4 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal-write$auto
detailed listing:
executing program 0:
r0 = openat$auto_kernfs_file_fops_kernfs_internal(0xffffffffffffff9c, &(0x7f0000000040)='/sys/devices/virtual/block/nbd9/queue/wbt_lat_usec\x00', 0x102e82, 0x0)
write$auto(r0, 0x0, 0x801)

program did not crash
extracting C reproducer
testing compiled C program (duration=45.396263044s, {Threaded:true Repeat:true RepeatTimes:0 Procs:4 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal-write$auto
program crashed: possible deadlock in static_key_slow_inc
a never seen crash title: possible deadlock in static_key_slow_inc, ignore
simplifying guilty program options
testing program (duration=45.396263044s, {Threaded:false Repeat:true RepeatTimes:0 Procs:4 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:true Cgroups:true BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal-write$auto
detailed listing:
executing program 0:
r0 = openat$auto_kernfs_file_fops_kernfs_internal(0xffffffffffffff9c, &(0x7f0000000040)='/sys/devices/virtual/block/nbd9/queue/wbt_lat_usec\x00', 0x102e82, 0x0)
write$auto(r0, &(0x7f0000000240)='0\x00\xa6\xcc\r\x91QU\x9dI\xda\x1b\xad\xb1\x9e\xc8Tt\xa8\x94\x9c\x8a\xe2\xc7cOM\xb6\xa3,!o\x9e\xb0\xadT\xfbR\xa1Y\x94V[8\x04c\xdf:]\xd9\x94\xf8F\xbb\xa2\xbb>\xade\x18\xbd\xe2\x1c\x89OO]e[\xbb\xf9\xcd\xc0\xc9\x00\xda\xac\xdd\x1a\xdd\xdd\xb9o\x1a\xab\xd5\xef\xc0\x04z\xd0I>\x8f\x00\xe5\x1c*\xed`\xfd\x15\x88\x0f\x9a\xd5\xa7\x14\f};\xabt\xd1ak\xe5\x98\xea\xe3}\x10\xab\f_\x19\x9b\x11\xb25VUK\x93\xcdd\x17\xe4\xcbA\xa5[\b\xb8;\x02tcf\x06\xfbD\x91\xcaG\xdaa:k[r\x06\xeb\xf0\x03\x00\x00\x00\x00\x00\x00\x00\xdeK\xa5\x8e\xd6\x8f\xd0UV\x11\xcb\xdd\x81\xbe\xdeL/\x06\xd5Y\a\xc1\xe9(\x95\xdfH\xf4\v\xf3C', 0x801)

program crashed: possible deadlock in static_key_slow_inc
a never seen crash title: possible deadlock in static_key_slow_inc, ignore
testing program (duration=45.396263044s, {Threaded:true Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:false Cgroups:false BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal-write$auto
detailed listing:
executing program 0:
r0 = openat$auto_kernfs_file_fops_kernfs_internal(0xffffffffffffff9c, &(0x7f0000000040)='/sys/devices/virtual/block/nbd9/queue/wbt_lat_usec\x00', 0x102e82, 0x0)
write$auto(r0, &(0x7f0000000240)='0\x00\xa6\xcc\r\x91QU\x9dI\xda\x1b\xad\xb1\x9e\xc8Tt\xa8\x94\x9c\x8a\xe2\xc7cOM\xb6\xa3,!o\x9e\xb0\xadT\xfbR\xa1Y\x94V[8\x04c\xdf:]\xd9\x94\xf8F\xbb\xa2\xbb>\xade\x18\xbd\xe2\x1c\x89OO]e[\xbb\xf9\xcd\xc0\xc9\x00\xda\xac\xdd\x1a\xdd\xdd\xb9o\x1a\xab\xd5\xef\xc0\x04z\xd0I>\x8f\x00\xe5\x1c*\xed`\xfd\x15\x88\x0f\x9a\xd5\xa7\x14\f};\xabt\xd1ak\xe5\x98\xea\xe3}\x10\xab\f_\x19\x9b\x11\xb25VUK\x93\xcdd\x17\xe4\xcbA\xa5[\b\xb8;\x02tcf\x06\xfbD\x91\xcaG\xdaa:k[r\x06\xeb\xf0\x03\x00\x00\x00\x00\x00\x00\x00\xdeK\xa5\x8e\xd6\x8f\xd0UV\x11\xcb\xdd\x81\xbe\xdeL/\x06\xd5Y\a\xc1\xe9(\x95\xdfH\xf4\v\xf3C', 0x801)

program crashed: possible deadlock in pcpu_alloc_noprof
extracting C reproducer
testing compiled C program (duration=45.396263044s, {Threaded:true Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox:none SandboxArg:0 Leak:false NetInjection:true NetDevices:true NetReset:false Cgroups:false BinfmtMisc:true CloseFDs:true KCSAN:false DevlinkPCI:false NicVF:false USB:true VhciInjection:true Wifi:true IEEE802154:true Sysctl:true Swap:true UseTmpDir:true HandleSegv:true Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}): openat$auto_kernfs_file_fops_kernfs_internal-write$auto
program crashed: possible deadlock in static_key_slow_inc
a never seen crash title: possible deadlock in static_key_slow_inc, ignore
reproducing took 13m12.892871474s
repro crashed as (corrupted=false):
======================================================
WARNING: possible circular locking dependency detected
6.15.0-syzkaller-07774-g90b83efa6701 #0 Not tainted
------------------------------------------------------
syz.0.16/6013 is trying to acquire lock:
ffffffff8e52d3a8 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0xb4a/0x1470 mm/percpu.c:1782

but task is already holding lock:
ffff888142fef608 (&q->q_usage_counter(io)#58){++++}-{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)#58){++++}-{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
       nbd_dev_add+0x4a0/0xbc0 drivers/block/nbd.c:1933
       nbd_init+0x181/0x320 drivers/block/nbd.c:2670
       do_one_initcall+0x120/0x6e0 init/main.c:1257
       do_initcall_level init/main.c:1319 [inline]
       do_initcalls init/main.c:1335 [inline]
       do_basic_setup init/main.c:1354 [inline]
       kernel_init_freeable+0x5c2/0x900 init/main.c:1567
       kernel_init+0x1c/0x2b0 init/main.c:1457
       ret_from_fork+0x5d7/0x6f0 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:4056 [inline]
       fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4070
       might_alloc include/linux/sched/mm.h:318 [inline]
       prepare_alloc_pages+0x162/0x610 mm/page_alloc.c:4738
       __alloc_frozen_pages_noprof+0x18b/0x23f0 mm/page_alloc.c:4959
       __alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:5004
       __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_mangle_table_init+0x40/0x60 net/ipv4/netfilter/iptable_mangle.c:92
       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:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       pcpu_alloc_noprof+0xb4a/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+0xef/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x6c7/0x1150 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)#58

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&q->q_usage_counter(io)#58);
                               lock(fs_reclaim);
                               lock(&q->q_usage_counter(io)#58);
  lock(pcpu_alloc_mutex);

 *** DEADLOCK ***

6 locks held by syz.0.16/6013:
 #0: ffff88803325fb38 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1213
 #1: ffff88807cdcc428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738
 #2: ffff88803232bc88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325
 #3: ffff88814336ec38 (kn->active#60){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326
 #4: ffff888142fef608 (&q->q_usage_counter(io)#58){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205
 #5: ffff888142fef640 (&q->q_usage_counter(queue)#10){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205

stack backtrace:
CPU: 0 UID: 0 PID: 6013 Comm: syz.0.16 Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __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:601 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
 pcpu_alloc_noprof+0xb4a/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+0xef/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x6c7/0x1150 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: 0033:0x7f6425b8e969
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:00007f64269f3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f6425db5fa0 RCX: 00007f6425b8e969
RDX: 0000000000000801 RSI: 0000200000000240 RDI: 0000000000000003
RBP: 00007f6425c10ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6425db5fa0 R15: 00007ffe18580788
 </TASK>

final repro crashed as (corrupted=false):
======================================================
WARNING: possible circular locking dependency detected
6.15.0-syzkaller-07774-g90b83efa6701 #0 Not tainted
------------------------------------------------------
syz.0.16/6013 is trying to acquire lock:
ffffffff8e52d3a8 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0xb4a/0x1470 mm/percpu.c:1782

but task is already holding lock:
ffff888142fef608 (&q->q_usage_counter(io)#58){++++}-{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)#58){++++}-{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
       nbd_dev_add+0x4a0/0xbc0 drivers/block/nbd.c:1933
       nbd_init+0x181/0x320 drivers/block/nbd.c:2670
       do_one_initcall+0x120/0x6e0 init/main.c:1257
       do_initcall_level init/main.c:1319 [inline]
       do_initcalls init/main.c:1335 [inline]
       do_basic_setup init/main.c:1354 [inline]
       kernel_init_freeable+0x5c2/0x900 init/main.c:1567
       kernel_init+0x1c/0x2b0 init/main.c:1457
       ret_from_fork+0x5d7/0x6f0 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:4056 [inline]
       fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4070
       might_alloc include/linux/sched/mm.h:318 [inline]
       prepare_alloc_pages+0x162/0x610 mm/page_alloc.c:4738
       __alloc_frozen_pages_noprof+0x18b/0x23f0 mm/page_alloc.c:4959
       __alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:5004
       __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_mangle_table_init+0x40/0x60 net/ipv4/netfilter/iptable_mangle.c:92
       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:601 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
       pcpu_alloc_noprof+0xb4a/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+0xef/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x6c7/0x1150 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)#58

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&q->q_usage_counter(io)#58);
                               lock(fs_reclaim);
                               lock(&q->q_usage_counter(io)#58);
  lock(pcpu_alloc_mutex);

 *** DEADLOCK ***

6 locks held by syz.0.16/6013:
 #0: ffff88803325fb38 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1213
 #1: ffff88807cdcc428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738
 #2: ffff88803232bc88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325
 #3: ffff88814336ec38 (kn->active#60){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326
 #4: ffff888142fef608 (&q->q_usage_counter(io)#58){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205
 #5: ffff888142fef640 (&q->q_usage_counter(queue)#10){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205

stack backtrace:
CPU: 0 UID: 0 PID: 6013 Comm: syz.0.16 Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __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:601 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
 pcpu_alloc_noprof+0xb4a/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+0xef/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x6c7/0x1150 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: 0033:0x7f6425b8e969
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:00007f64269f3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f6425db5fa0 RCX: 00007f6425b8e969
RDX: 0000000000000801 RSI: 0000200000000240 RDI: 0000000000000003
RBP: 00007f6425c10ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6425db5fa0 R15: 00007ffe18580788
 </TASK>