INFO: rcu detected stall in l2cap_sock_release

Status: auto-obsoleted due to no activity on 2026/09/08 23:47
Subsystems: bluetooth
Labels: prio:high
[Documentation on labels]
First crash: 105d, last: 105d
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ID Workflow Result Correct Bug Created Started Finished Revision
a685aebb assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ✅ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in l2cap_sock_release 2026/06/12 00:03 2026/06/12 00:03 2026/06/12 00:32 d93a6ab6

Sample crash report:
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=10502 jiffies, g=254589, q=1127 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 3522 (4295097129-4295093607), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 3523 jiffies! g254589 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27536 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x1821/0x5740 kernel/sched/core.c:7189
 __schedule_loop kernel/sched/core.c:7268 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7283
 schedule_timeout+0x158/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x312/0x11d0 kernel/rcu/tree.c:2095
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2297
 kthread+0x389/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 3212 Comm: krfcommd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:37 [inline]
RIP: 0010:trace_lock_release include/trace/events/lock.h:69 [inline]
RIP: 0010:lock_release+0x25/0x3c0 kernel/locking/lockdep.c:5879
Code: 90 90 90 90 90 f3 0f 1e fa 55 41 57 41 56 41 55 41 54 53 48 83 ec 30 49 89 f5 49 89 fe 65 48 8b 05 20 2b 96 11 48 89 44 24 28 <0f> 1f 44 00 00 65 8b 05 23 2b 96 11 83 f8 08 0f 83 56 02 00 00 89
RSP: 0018:ffffc900000069b0 EFLAGS: 00000282
RAX: dc1ef1daf08ce800 RBX: 0000000000000000 RCX: 0000000080000101
RDX: ffffffff90bf169e RSI: ffffffff8176e256 RDI: ffffffff8e95cc20
RBP: dffffc0000000000 R08: 000000000000001e R09: ffffffff8e95cc20
R10: ffffc90000006b38 R11: ffffffff81b0e0e0 R12: ffffffff90bf16a2
R13: ffffffff8176e256 R14: ffffffff8e95cc20 R15: ffffffff8176e256
FS:  0000000000000000(0000) GS:ffff8881252a0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2e59d456b8 CR3: 00000000aa222000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 rcu_lock_release include/linux/rcupdate.h:310 [inline]
 rcu_read_unlock include/linux/rcupdate.h:869 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1181 [inline]
 unwind_next_frame+0x1bba/0x2550 arch/x86/kernel/unwind_orc.c:709
 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6251 [inline]
 kmem_cache_free+0x182/0x650 mm/slub.c:6378
 kfree_skb_reason include/linux/skbuff.h:1324 [inline]
 kfree_skb include/linux/skbuff.h:1333 [inline]
 ip6_mc_input+0x8de/0xbd0 net/ipv6/ip6_input.c:638
 ip_sabotage_in+0x1e1/0x270 net/bridge/br_netfilter_hooks.c:988
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x21f/0x3c0 include/linux/netfilter.h:316
 __netif_receive_skb_one_core net/core/dev.c:6202 [inline]
 __netif_receive_skb net/core/dev.c:6315 [inline]
 netif_receive_skb_internal net/core/dev.c:6401 [inline]
 netif_receive_skb+0x278/0xbf0 net/core/dev.c:6460
 NF_HOOK+0xa4/0x3a0 include/linux/netfilter.h:318
 br_handle_frame_finish+0x1541/0x1c80 net/bridge/br_input.c:-1
 br_nf_hook_thresh+0x3dd/0x4c0 net/bridge/br_netfilter_hooks.c:-1
 br_nf_pre_routing_finish_ipv6+0x91f/0xc30 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:318 [inline]
 br_nf_pre_routing_ipv6+0x374/0x6f0 net/bridge/br_netfilter_ipv6.c:183
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0x1277/0x1510 net/bridge/br_input.c:442
 __netif_receive_skb_core+0x98f/0x3170 net/core/dev.c:6089
 __netif_receive_skb_one_core net/core/dev.c:6200 [inline]
 __netif_receive_skb net/core/dev.c:6315 [inline]
 process_backlog+0x76d/0x1950 net/core/dev.c:6666
 __napi_poll+0xae/0x340 net/core/dev.c:7733
 napi_poll net/core/dev.c:7796 [inline]
 net_rx_action+0x627/0xf70 net/core/dev.c:7953
 handle_softirqs+0x22a/0x840 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:stack_trace_consume_entry+0x56/0x280 kernel/stacktrace.c:89
Code: 84 c0 0f 85 09 01 00 00 44 8b 4f 10 4c 8d 77 08 4d 89 f5 49 c1 ed 03 41 0f b6 44 15 00 84 c0 0f 85 22 01 00 00 45 3b 0e 73 3a <48> 8d 5f 0c 49 89 df 49 c1 ef 03 41 0f b6 04 17 84 c0 0f 85 47 01
RSP: 0018:ffffc9000de8e778 EFLAGS: 00000283
RAX: 0000000000000000 RBX: ffffc9000de8e880 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: ffffffff8aa8cec2 RDI: ffffc9000de8e880
RBP: 1ffff92001bd1d12 R08: ffffc9000de8e890 R09: 0000000000000001
R10: ffffc9000de8e818 R11: ffffffff81b0e0e0 R12: ffff88803213dd00
R13: 1ffff92001bd1d11 R14: ffffc9000de8e888 R15: ffffc9000de8e7c8
 arch_stack_walk+0x10f/0x150 arch/x86/kernel/stacktrace.c:27
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 ref_tracker_free+0x11e/0x840 lib/ref_tracker.c:306
 __netns_tracker_free include/net/net_namespace.h:384 [inline]
 __sk_destruct+0x7a8/0x9d0 net/core/sock.c:2388
 l2cap_sock_release+0x192/0x230 net/bluetooth/l2cap_sock.c:1468
 __sock_release net/socket.c:722 [inline]
 sock_release+0x85/0x150 net/socket.c:750
 rfcomm_session_del+0x18b/0x2c0 net/bluetooth/rfcomm/core.c:721
 rfcomm_process_rx+0x6b0d/0x6c80 net/bluetooth/rfcomm/core.c:1988
 rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2073 [inline]
 rfcomm_run+0xb3c/0x30c0 net/bluetooth/rfcomm/core.c:2161
 kthread+0x389/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
net_ratelimit: 8365 callbacks suppressed
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:1c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:1c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
net_ratelimit: 12191 callbacks suppressed
bridge0: received packet on veth1_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_1 with own address as source address (addr:aa:aa:aa:aa:aa:1c, vlan:0)

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/10 23:44 net 627366c51145 f79bac11 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in l2cap_sock_release
* Struck through repros no longer work on HEAD.