Re: [syzbot] [batman?] [bpf?] possible deadlock in lock_timer_base

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    35c3e2791756 Revert "net: Re-use and set mono_delivery_tim..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=10569181180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=8983d6d4f7df556be565
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13d9fa4e180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=137afac9180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/26b55a26fc12/disk-35c3e279.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6f39fa55c828/vmlinux-35c3e279.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e1e0501539e6/bzImage-35c3e279.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8983d6d4f7df556be565@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
6.8.0-syzkaller-05228-g35c3e2791756 #0 Not tainted
-----------------------------------------------------
rcu_preempt/16 [HC0[0]:SC0[2]:HE0:SE0] is trying to acquire:
ffff888021c65020 (&htab->buckets[i].lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888021c65020 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939

and this task is already holding:
ffff8880b952a758
 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x112/0x240 kernel/time/timer.c:1051
which would create a new lock dependency:
 (&base->lock){-.-.}-{2:2} -> (
&htab->buckets[i].lock){+...}-{2:2}

but this new dependency connects a HARDIRQ-irq-safe lock:
 (&base->lock){-.-.}-{2:2}

.. which became HARDIRQ-irq-safe at:
  lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
  lock_timer_base+0x112/0x240 kernel/time/timer.c:1051
  add_timer_on+0x1e5/0x5c0 kernel/time/timer.c:1366
  handle_irq_event_percpu kernel/irq/handle.c:195 [inline]
  handle_irq_event+0xad/0x1f0 kernel/irq/handle.c:210
  handle_level_irq+0x3c5/0x6e0 kernel/irq/chip.c:648
  generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
  handle_irq arch/x86/kernel/irq.c:238 [inline]
  __common_interrupt+0x13a/0x230 arch/x86/kernel/irq.c:257
  common_interrupt+0xa5/0xd0 arch/x86/kernel/irq.c:247
  asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
  _raw_spin_unlock_irqrestore+0xd8/0x140 kernel/locking/spinlock.c:194
  __setup_irq+0x1277/0x1cf0 kernel/irq/manage.c:1818
  request_threaded_irq+0x2ab/0x380 kernel/irq/manage.c:2202
  request_irq include/linux/interrupt.h:168 [inline]
  setup_default_timer_irq+0x25/0x60 arch/x86/kernel/time.c:70
  x86_late_time_init+0x66/0xc0 arch/x86/kernel/time.c:94
  start_kernel+0x3f3/0x500 init/main.c:1039
  x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:509
  x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:490
  common_startup_64+0x13e/0x147

to a HARDIRQ-irq-unsafe lock:
 (&htab->buckets[i].lock){+...}-{2:2}

.. which became HARDIRQ-irq-unsafe at:
..
  lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
  __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
  _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
  spin_lock_bh include/linux/spinlock.h:356 [inline]
  sock_hash_free+0x164/0x820 net/core/sock_map.c:1154
  bpf_map_free_deferred+0xe6/0x110 kernel/bpf/syscall.c:734
  process_one_work kernel/workqueue.c:3254 [inline]
  process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
  worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
  kthread+0x2f0/0x390 kernel/kthread.c:388
  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

other info that might help us debug this:

 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&htab->buckets[i].lock
);
                               local_irq_disable();
                               lock(&base->lock);
                               lock(&htab->buckets[i].lock
);
  <Interrupt>
    lock(&base->lock);

 *** DEADLOCK ***

2 locks held by rcu_preempt/16:
 #0: 
ffff8880b952a758
 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x112/0x240 kernel/time/timer.c:1051
 #1: ffffffff8e131920
 (rcu_read_lock
){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420

the dependencies between HARDIRQ-irq-safe lock and the holding lock:
-> (&base->lock){-.-.}-{2:2} {
   IN-HARDIRQ-W at:
                    lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
                    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                    _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
                    lock_timer_base+0x112/0x240 kernel/time/timer.c:1051
                    add_timer_on+0x1e5/0x5c0 kernel/time/timer.c:1366
                    handle_irq_event_percpu kernel/irq/handle.c:195 [inline]
                    handle_irq_event+0xad/0x1f0 kernel/irq/handle.c:210
                    handle_level_irq+0x3c5/0x6e0 kernel/irq/chip.c:648
                    generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
                    handle_irq arch/x86/kernel/irq.c:238 [inline]
                    __common_interrupt+0x13a/0x230 arch/x86/kernel/irq.c:257
                    common_interrupt+0xa5/0xd0 arch/x86/kernel/irq.c:247
                    asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
                    __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
                    _raw_spin_unlock_irqrestore+0xd8/0x140 kernel/locking/spinlock.c:194
                    __setup_irq+0x1277/0x1cf0 kernel/irq/manage.c:1818
                    request_threaded_irq+0x2ab/0x380 kernel/irq/manage.c:2202
                    request_irq include/linux/interrupt.h:168 [inline]
                    setup_default_timer_irq+0x25/0x60 arch/x86/kernel/time.c:70
                    x86_late_time_init+0x66/0xc0 arch/x86/kernel/time.c:94
                    start_kernel+0x3f3/0x500 init/main.c:1039
                    x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:509
                    x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:490
                    common_startup_64+0x13e/0x147
   IN-SOFTIRQ-W at:
                    lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
                    __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
                    _raw_spin_lock_irq+0xd3/0x120 kernel/locking/spinlock.c:170
                    __run_timer_base+0x103/0x8e0 kernel/time/timer.c:2418
                    run_timer_base kernel/time/timer.c:2428 [inline]
                    run_timer_softirq+0x67/0x170 kernel/time/timer.c:2436
                    __do_softirq+0x2be/0x943 kernel/softirq.c:554
                    invoke_softirq kernel/softirq.c:428 [inline]
                    __irq_exit_rcu+0xf2/0x1c0 kernel/softirq.c:633
                    irq_exit_rcu+0x9/0x30 kernel/softirq.c:645
                    common_interrupt+0xaa/0xd0 arch/x86/kernel/irq.c:247
                    asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:693
                    console_flush_all+0x9cd/0xec0
                    console_unlock+0x13b/0x4d0 kernel/printk/printk.c:3025
                    vprintk_emit+0x509/0x720 kernel/printk/printk.c:2292
                    _printk+0xd5/0x120 kernel/printk/printk.c:2317
                    cpu_select_mitigations+0x3c/0xa0 arch/x86/kernel/cpu/bugs.c:148
                    arch_cpu_finalize_init+0x20/0xa0 arch/x86/kernel/cpu/common.c:2325
                    start_kernel+0x402/0x500 init/main.c:1043
                    x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:509
                    x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:490
                    common_startup_64+0x13e/0x147
   INITIAL USE
 at:
                   lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
                   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                   _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
                   lock_timer_base+0x112/0x240 kernel/time/timer.c:1051
                   __mod_timer+0x1ca/0xeb0 kernel/time/timer.c:1132
                   queue_delayed_work_on+0x15a/0x260 kernel/workqueue.c:2595
                   queue_delayed_work include/linux/workqueue.h:620 [inline]
                   crng_reseed+0xe7/0x220 drivers/char/random.c:258
                   random_init+0x1a9/0x300 drivers/char/random.c:901
                   start_kernel+0x253/0x500 init/main.c:991
                   x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:509
                   x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:490
                   common_startup_64+0x13e/0x147
 }
 ... key      at: [<ffffffff945023c0>] init_timer_cpu.__key+0x0/0x20

the dependencies between the lock to be acquired
 and HARDIRQ-irq-unsafe lock:
->
 (&htab->buckets[i].lock
){+...}-{2:2} {
   HARDIRQ-ON-W at:
                    lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
                    __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
                    _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
                    spin_lock_bh include/linux/spinlock.h:356 [inline]
                    sock_hash_free+0x164/0x820 net/core/sock_map.c:1154
                    bpf_map_free_deferred+0xe6/0x110 kernel/bpf/syscall.c:734
                    process_one_work kernel/workqueue.c:3254 [inline]
                    process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
                    worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
                    kthread+0x2f0/0x390 kernel/kthread.c:388
                    ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
                    ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
   INITIAL USE
 at:
                   lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
                   __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
                   _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
                   spin_lock_bh include/linux/spinlock.h:356 [inline]
                   sock_hash_free+0x164/0x820 net/core/sock_map.c:1154
                   bpf_map_free_deferred+0xe6/0x110 kernel/bpf/syscall.c:734
                   process_one_work kernel/workqueue.c:3254 [inline]
                   process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
                   worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
                   kthread+0x2f0/0x390 kernel/kthread.c:388
                   ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
                   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
 }
 ... key      at: [<ffffffff94882300>] sock_hash_alloc.__key+0x0/0x20
 ... acquired at:
   lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
   __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
   _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
   spin_lock_bh include/linux/spinlock.h:356 [inline]
   sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
   bpf_prog_2c29ac5cdc6b1842+0x42/0x46
   bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
   __bpf_prog_run include/linux/filter.h:657 [inline]
   bpf_prog_run include/linux/filter.h:664 [inline]
   __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
   bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
   trace_timer_start include/trace/events/timer.h:52 [inline]
   enqueue_timer+0x396/0x550 kernel/time/timer.c:663
   internal_add_timer kernel/time/timer.c:688 [inline]
   __mod_timer+0xa0e/0xeb0 kernel/time/timer.c:1183
   schedule_timeout+0x1b9/0x310 kernel/time/timer.c:2571
   rcu_gp_fqs_loop+0x2df/0x1370 kernel/rcu/tree.c:1663
   rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:1862
   kthread+0x2f0/0x390 kernel/kthread.c:388
   ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243


stack backtrace:
CPU: 1 PID: 16 Comm: rcu_preempt Not tainted 6.8.0-syzkaller-05228-g35c3e2791756 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
 print_bad_irq_dependency kernel/locking/lockdep.c:2626 [inline]
 check_irq_usage kernel/locking/lockdep.c:2865 [inline]
 check_prev_add kernel/locking/lockdep.c:3138 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain+0x4dc7/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
 bpf_prog_2c29ac5cdc6b1842+0x42/0x46
 bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
 __bpf_prog_run include/linux/filter.h:657 [inline]
 bpf_prog_run include/linux/filter.h:664 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
 bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
 trace_timer_start include/trace/events/timer.h:52 [inline]
 enqueue_timer+0x396/0x550 kernel/time/timer.c:663
 internal_add_timer kernel/time/timer.c:688 [inline]
 __mod_timer+0xa0e/0xeb0 kernel/time/timer.c:1183
 schedule_timeout+0x1b9/0x310 kernel/time/timer.c:2571
 rcu_gp_fqs_loop+0x2df/0x1370 kernel/rcu/tree.c:1663
 rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:1862
 kthread+0x2f0/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
 </TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.