Subject: [syzbot] [bpf?] possible deadlock in work_grab_pending (2)

From: syzbot <[email-masked]>
Date: Tue, 05 Nov 2024 23:14:19 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    dbb9a7ef3478 net: fjes: use ethtool string helpers
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1733c987980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a9d1c42858837b59
dashboard link: https://syzkaller.appspot.com/bug?extid=ae3633ca70dce1eee4e1
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/df61ec56738e/disk-dbb9a7ef.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6ad9020b8df8/vmlinux-dbb9a7ef.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d1b9e903e0c9/bzImage-dbb9a7ef.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc5-syzkaller-01053-gdbb9a7ef3478 #0 Not tainted
------------------------------------------------------
syz.4.2526/15232 is trying to acquire lock:
ffff88801aca0018 (&pool->lock){-.-.}-{2:2}, at: try_to_grab_pending kernel/workqueue.c:2081 [inline]
ffff88801aca0018 (&pool->lock){-.-.}-{2:2}, at: work_grab_pending+0x294/0xae0 kernel/workqueue.c:2157

but task is already holding lock:
ffff8880b8729430 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:3312 [inline]
ffff8880b8729430 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3725 [inline]
ffff8880b8729430 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x18a/0x790 kernel/rcu/tree.c:3811

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (krc.lock){..-.}-{2:2}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       krc_this_cpu_lock kernel/rcu/tree.c:3312 [inline]
       add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3725 [inline]
       kvfree_call_rcu+0x18a/0x790 kernel/rcu/tree.c:3811
       trie_delete_elem+0x546/0x6a0 kernel/bpf/lpm_trie.c:540
       0xffffffffa000206f
       bpf_dispatcher_nop_func include/linux/bpf.h:1265 [inline]
       __bpf_prog_run include/linux/filter.h:701 [inline]
       bpf_prog_run include/linux/filter.h:708 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2316 [inline]
       bpf_trace_run4+0x334/0x590 kernel/trace/bpf_trace.c:2359
       __traceiter_sched_switch+0x98/0xd0 include/trace/events/sched.h:222
       trace_sched_switch include/trace/events/sched.h:222 [inline]
       __schedule+0x2340/0x4bd0 kernel/sched/core.c:6687
       preempt_schedule_common+0x84/0xd0 kernel/sched/core.c:6869
       preempt_schedule+0xe1/0xf0 kernel/sched/core.c:6893
       preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk.S:12
       class_preempt_destructor include/linux/preempt.h:480 [inline]
       try_to_wake_up+0x9f3/0x14b0 kernel/sched/core.c:4288
       wake_up_process kernel/sched/core.c:4414 [inline]
       wake_up_q+0xc8/0x120 kernel/sched/core.c:1067
       futex_wake+0x523/0x5c0 kernel/futex/waitwake.c:199
       do_futex+0x392/0x560 kernel/futex/syscalls.c:107
       __do_sys_futex kernel/futex/syscalls.c:179 [inline]
       __se_sys_futex+0x3f9/0x480 kernel/futex/syscalls.c:160
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&rq->__lock){-.-.}-{2:2}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       _raw_spin_lock_nested+0x31/0x40 kernel/locking/spinlock.c:378
       raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:598
       raw_spin_rq_lock kernel/sched/sched.h:1505 [inline]
       task_rq_lock+0xc6/0x360 kernel/sched/core.c:700
       cgroup_move_task+0x9b/0x5a0 kernel/sched/psi.c:1161
       css_set_move_task+0x72e/0x950 kernel/cgroup/cgroup.c:898
       cgroup_post_fork+0x256/0x880 kernel/cgroup/cgroup.c:6692
       copy_process+0x39e9/0x3d50 kernel/fork.c:2598
       kernel_clone+0x226/0x8f0 kernel/fork.c:2784
       user_mode_thread+0x132/0x1a0 kernel/fork.c:2862
       rest_init+0x23/0x300 init/main.c:712
       start_kernel+0x47f/0x500 init/main.c:1105
       x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:507
       x86_64_start_kernel+0x9f/0xa0 arch/x86/kernel/head64.c:488
       common_startup_64+0x13e/0x147

-> #1 (&p->pi_lock){-.-.}-{2:2}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
       class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:551 [inline]
       try_to_wake_up+0xbe/0x14b0 kernel/sched/core.c:4165
       create_worker+0x507/0x720 kernel/workqueue.c:2825
       workqueue_init+0x520/0x8a0 kernel/workqueue.c:7902
       kernel_init_freeable+0x3fe/0x5d0 init/main.c:1564
       kernel_init+0x1d/0x2b0 init/main.c:1469
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (&pool->lock){-.-.}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       try_to_grab_pending kernel/workqueue.c:2081 [inline]
       work_grab_pending+0x294/0xae0 kernel/workqueue.c:2157
       mod_delayed_work_on+0xd4/0x370 kernel/workqueue.c:2585
       kvfree_call_rcu+0x47f/0x790 kernel/rcu/tree.c:3839
       trie_update_elem+0x7e5/0xc00 kernel/bpf/lpm_trie.c:441
       bpf_map_update_value+0x4d3/0x540 kernel/bpf/syscall.c:203
       generic_map_update_batch+0x60d/0x900 kernel/bpf/syscall.c:1849
       bpf_map_do_batch+0x39a/0x660 kernel/bpf/syscall.c:5162
       __sys_bpf+0x377/0x810
       __do_sys_bpf kernel/bpf/syscall.c:5760 [inline]
       __se_sys_bpf kernel/bpf/syscall.c:5758 [inline]
       __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5758
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &pool->lock --> &rq->__lock --> krc.lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(krc.lock);
                               lock(&rq->__lock);
                               lock(krc.lock);
  lock(&pool->lock);

 *** DEADLOCK ***

3 locks held by syz.4.2526/15232:
 #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: bpf_map_update_value+0x3c4/0x540 kernel/bpf/syscall.c:202
 #1: ffff8880b8729430 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:3312 [inline]
 #1: ffff8880b8729430 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3725 [inline]
 #1: ffff8880b8729430 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x18a/0x790 kernel/rcu/tree.c:3811
 #2: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #2: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #2: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: try_to_grab_pending kernel/workqueue.c:2072 [inline]
 #2: ffffffff8e937da0 (rcu_read_lock){....}-{1:2}, at: work_grab_pending+0x1d3/0xae0 kernel/workqueue.c:2157

stack backtrace:
CPU: 1 UID: 0 PID: 15232 Comm: syz.4.2526 Not tainted 6.12.0-rc5-syzkaller-01053-gdbb9a7ef3478 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 try_to_grab_pending kernel/workqueue.c:2081 [inline]
 work_grab_pending+0x294/0xae0 kernel/workqueue.c:2157
 mod_delayed_work_on+0xd4/0x370 kernel/workqueue.c:2585
 kvfree_call_rcu+0x47f/0x790 kernel/rcu/tree.c:3839
 trie_update_elem+0x7e5/0xc00 kernel/bpf/lpm_trie.c:441
 bpf_map_update_value+0x4d3/0x540 kernel/bpf/syscall.c:203
 generic_map_update_batch+0x60d/0x900 kernel/bpf/syscall.c:1849
 bpf_map_do_batch+0x39a/0x660 kernel/bpf/syscall.c:5162
 __sys_bpf+0x377/0x810
 __do_sys_bpf kernel/bpf/syscall.c:5760 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5758 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5758
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdcb177e719
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:00007fdcb2645038 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fdcb1935f80 RCX: 00007fdcb177e719
RDX: 0000000000000038 RSI: 0000000020000000 RDI: 000000000000001a
RBP: 00007fdcb17f132e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fdcb1935f80 R15: 00007ffe264ea148
 </TASK>

---
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