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possible deadlock in htab_lock_bucket

Status: upstream: reported syz repro on 2025/10/28 07:33
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+b41573d719ff7fa9f894@syzkaller.appspotmail.com
First crash: 90d, last: 8d04h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/01/18 linux-6.6.y (ToT) cbb31f77b879 syz [report] possible deadlock in htab_lock_bucket
2026/01/18 upstream (ToT) e84d960149e7 syz Didn't crash
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in htab_lock_bucket (2) bpf 4 C error error 6 307d 539d 0/29 auto-obsoleted due to no activity on 2025/08/26 22:14
linux-6.1 possible deadlock in htab_lock_bucket origin:upstream missing-backport 4 C inconclusive 11 58d 649d 0/3 upstream: reported C repro on 2024/04/17 13:40
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/01/22 12:13 1m fix candidate upstream error job log

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u4:9/3458 is trying to acquire lock:
ffff88805decdca0 (&htab->lockdep_key#4){....}-{2:2}, at: htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166

but task is already holding lock:
ffff88805dc39720 (&htab->lockdep_key#3){-...}-{2:2}, at: htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&htab->lockdep_key#3){-...}-{2:2}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166
       htab_map_delete_elem+0x1a4/0x630 kernel/bpf/hashtab.c:1443
       bpf_prog_2c29ac5cdc6b1842+0x42/0x46
       bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
       __bpf_prog_run include/linux/filter.h:612 [inline]
       bpf_prog_run include/linux/filter.h:619 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
       bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
       __bpf_trace_contention_end+0xdd/0x130 include/trace/events/lock.h:122
       __traceiter_contention_end+0x78/0xb0 include/trace/events/lock.h:122
       trace_contention_end+0xe6/0x110 include/trace/events/lock.h:122
       __pv_queued_spin_lock_slowpath+0x7ec/0x9d0 kernel/locking/qspinlock.c:560
       pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:586 [inline]
       queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
       queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
       do_raw_spin_lock+0x24e/0x2c0 kernel/locking/spinlock_debug.c:115
       htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166
       htab_map_delete_elem+0x1a4/0x630 kernel/bpf/hashtab.c:1443
       bpf_prog_2c29ac5cdc6b1842+0x42/0x46
       bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
       __bpf_prog_run include/linux/filter.h:612 [inline]
       bpf_prog_run include/linux/filter.h:619 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
       bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
       __bpf_trace_contention_end+0xdd/0x130 include/trace/events/lock.h:122
       __traceiter_contention_end+0x78/0xb0 include/trace/events/lock.h:122
       trace_contention_end+0xc5/0xe0 include/trace/events/lock.h:122
       __mutex_lock_common kernel/locking/mutex.c:612 [inline]
       __mutex_lock+0x2fa/0xcc0 kernel/locking/mutex.c:747
       sdata_lock net/mac80211/ieee80211_i.h:1135 [inline]
       ieee80211_ibss_rx_queued_mgmt+0x11f/0x2ac0 net/mac80211/ibss.c:1631
       ieee80211_iface_process_skb net/mac80211/iface.c:1651 [inline]
       ieee80211_iface_work+0x717/0xc70 net/mac80211/iface.c:1705
       cfg80211_wiphy_work+0x225/0x260 net/wireless/core.c:437
       process_one_work kernel/workqueue.c:2634 [inline]
       process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
       worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
       kthread+0x2fa/0x390 kernel/kthread.c:388
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

-> #0 (&htab->lockdep_key#4){....}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
       lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
       __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166
       htab_map_delete_elem+0x1a4/0x630 kernel/bpf/hashtab.c:1443
       bpf_prog_2c29ac5cdc6b1842+0x42/0x46
       bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
       __bpf_prog_run include/linux/filter.h:612 [inline]
       bpf_prog_run include/linux/filter.h:619 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
       bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
       __bpf_trace_contention_end+0xdd/0x130 include/trace/events/lock.h:122
       __traceiter_contention_end+0x78/0xb0 include/trace/events/lock.h:122
       trace_contention_end+0xe6/0x110 include/trace/events/lock.h:122
       __pv_queued_spin_lock_slowpath+0x7ec/0x9d0 kernel/locking/qspinlock.c:560
       pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:586 [inline]
       queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
       queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
       do_raw_spin_lock+0x24e/0x2c0 kernel/locking/spinlock_debug.c:115
       htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166
       htab_map_delete_elem+0x1a4/0x630 kernel/bpf/hashtab.c:1443
       bpf_prog_2c29ac5cdc6b1842+0x42/0x46
       bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
       __bpf_prog_run include/linux/filter.h:612 [inline]
       bpf_prog_run include/linux/filter.h:619 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
       bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
       __bpf_trace_contention_end+0xdd/0x130 include/trace/events/lock.h:122
       __traceiter_contention_end+0x78/0xb0 include/trace/events/lock.h:122
       trace_contention_end+0xc5/0xe0 include/trace/events/lock.h:122
       __mutex_lock_common kernel/locking/mutex.c:612 [inline]
       __mutex_lock+0x2fa/0xcc0 kernel/locking/mutex.c:747
       sdata_lock net/mac80211/ieee80211_i.h:1135 [inline]
       ieee80211_ibss_work+0xa4/0x10c0 net/mac80211/ibss.c:1684
       cfg80211_wiphy_work+0x225/0x260 net/wireless/core.c:437
       process_one_work kernel/workqueue.c:2634 [inline]
       process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
       worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
       kthread+0x2fa/0x390 kernel/kthread.c:388
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&htab->lockdep_key#3);
                               lock(&htab->lockdep_key#4);
                               lock(&htab->lockdep_key#3);
  lock(&htab->lockdep_key#4);

 *** DEADLOCK ***

7 locks held by kworker/u4:9/3458:
 #0: ffff888017871538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #0: ffff888017871538 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #1: ffffc9000cd57d00 ((work_completion)(&rdev->wiphy_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2609 [inline]
 #1: ffffc9000cd57d00 ((work_completion)(&rdev->wiphy_work)){+.+.}-{0:0}, at: process_scheduled_works+0x957/0x15b0 kernel/workqueue.c:2711
 #2: ffff888025248768 (&rdev->wiphy.mtx){+.+.}-{3:3}, at: wiphy_lock include/net/cfg80211.h:5777 [inline]
 #2: ffff888025248768 (&rdev->wiphy.mtx){+.+.}-{3:3}, at: cfg80211_wiphy_work+0x35/0x260 net/wireless/core.c:424
 #3: ffff88802489cd40 (&wdev->mtx){+.+.}-{3:3}, at: sdata_lock net/mac80211/ieee80211_i.h:1135 [inline]
 #3: ffff88802489cd40 (&wdev->mtx){+.+.}-{3:3}, at: ieee80211_ibss_work+0xa4/0x10c0 net/mac80211/ibss.c:1684
 #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2321 [inline]
 #4: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0xde/0x3c0 kernel/trace/bpf_trace.c:2361
 #5: ffff88805dc39720 (&htab->lockdep_key#3){-...}-{2:2}, at: htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166
 #6: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #6: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #6: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2321 [inline]
 #6: ffffffff8cd2ff20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0xde/0x3c0 kernel/trace/bpf_trace.c:2361

stack backtrace:
CPU: 1 PID: 3458 Comm: kworker/u4:9 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound cfg80211_wiphy_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 check_noncircular+0x2bd/0x3c0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166
 htab_map_delete_elem+0x1a4/0x630 kernel/bpf/hashtab.c:1443
 bpf_prog_2c29ac5cdc6b1842+0x42/0x46
 bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
 __bpf_prog_run include/linux/filter.h:612 [inline]
 bpf_prog_run include/linux/filter.h:619 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
 bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
 __bpf_trace_contention_end+0xdd/0x130 include/trace/events/lock.h:122
 __traceiter_contention_end+0x78/0xb0 include/trace/events/lock.h:122
 trace_contention_end+0xe6/0x110 include/trace/events/lock.h:122
 __pv_queued_spin_lock_slowpath+0x7ec/0x9d0 kernel/locking/qspinlock.c:560
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:586 [inline]
 queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
 queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
 do_raw_spin_lock+0x24e/0x2c0 kernel/locking/spinlock_debug.c:115
 htab_lock_bucket+0x181/0x300 kernel/bpf/hashtab.c:166
 htab_map_delete_elem+0x1a4/0x630 kernel/bpf/hashtab.c:1443
 bpf_prog_2c29ac5cdc6b1842+0x42/0x46
 bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
 __bpf_prog_run include/linux/filter.h:612 [inline]
 bpf_prog_run include/linux/filter.h:619 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
 bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
 __bpf_trace_contention_end+0xdd/0x130 include/trace/events/lock.h:122
 __traceiter_contention_end+0x78/0xb0 include/trace/events/lock.h:122
 trace_contention_end+0xc5/0xe0 include/trace/events/lock.h:122
 __mutex_lock_common kernel/locking/mutex.c:612 [inline]
 __mutex_lock+0x2fa/0xcc0 kernel/locking/mutex.c:747
 sdata_lock net/mac80211/ieee80211_i.h:1135 [inline]
 ieee80211_ibss_work+0xa4/0x10c0 net/mac80211/ibss.c:1684
 cfg80211_wiphy_work+0x225/0x260 net/wireless/core.c:437
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/26 22:13 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan possible deadlock in htab_lock_bucket
2025/11/13 00:11 linux-6.6.y 0a805b6ea8cd 07e030de .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in htab_lock_bucket
2025/11/12 21:53 linux-6.6.y 0a805b6ea8cd 07e030de .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in htab_lock_bucket
2025/11/10 23:26 linux-6.6.y 0a805b6ea8cd 4e1406b4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in htab_lock_bucket
2025/11/10 20:55 linux-6.6.y 0a805b6ea8cd 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in htab_lock_bucket
2025/10/28 07:33 linux-6.6.y 4a243110dc88 fd2207e7 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf possible deadlock in htab_lock_bucket
* Struck through repros no longer work on HEAD.