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* [syzbot] [bridge?] INFO: rcu detected stall in br_handle_frame (6)
@ 2026-01-13 18:06 syzbot
  2026-08-11 13:43 ` Forwarded: [syz test] net/sched: taprio: reject too-small software schedule intervals syzbot
  0 siblings, 1 reply; 4+ messages in thread
From: syzbot @ 2026-01-13 18:06 UTC (permalink / raw)
  To: bridge, coreteam, davem, edumazet, fw, horms, idosch, kadlec,
	kuba, linux-kernel, netdev, netfilter-devel, pabeni, pablo, phil,
	razor, syzkaller-bugs

Hello,

syzbot found the following issue on:

HEAD commit:    f83a4f2a4d8c Merge tag 'erofs-for-6.17-rc6-fixes' of git:/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17d98762580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4d8792ecb6308d0f
dashboard link: https://syzkaller.appspot.com/bug?extid=f8850bc3986562f79619
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=102d3b62580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=174fb934580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/446b6da00381/disk-f83a4f2a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/acc2d4e8a1cc/vmlinux-f83a4f2a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cec01f1ca35a/bzImage-f83a4f2a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8850bc3986562f79619@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (2 ticks this GP) idle=e7fc/1/0x4000000000000000 softirq=18961/18961 fqs=0
rcu: 	(detected by 1, t=10502 jiffies, g=12417, q=367 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 807 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: ipv6_addrconf addrconf_dad_work
RIP: 0010:taprio_set_budgets+0x12b/0x3b0 net/sched/sch_taprio.c:671
Code: e8 48 c1 e8 03 48 89 44 24 10 31 db 45 31 e4 4c 89 6c 24 18 bf 10 00 00 00 4c 89 e6 e8 8e 70 24 f8 49 83 fc 0f 48 89 6c 24 30 <0f> 87 8a 01 00 00 4d 8d 2c 2f 4c 89 e8 48 c1 e8 03 48 b9 00 00 00
RSP: 0018:ffffc90000006060 EFLAGS: 00000093
RAX: ffffffff899b5352 RBX: 0000000000000000 RCX: ffff88802481bc00
RDX: 0000000000010100 RSI: 0000000000000000 RDI: 0000000000000010
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000000c08 R12: 0000000000000000
R13: ffff8880313e32e0 R14: ffff8880743df930 R15: ffff8880743dfc00
FS:  0000000000000000(0000) GS:ffff888125c15000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055556d266808 CR3: 000000007e704000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 advance_sched+0x963/0xc90 net/sched/sch_taprio.c:982
 __run_hrtimer kernel/time/hrtimer.c:1761 [inline]
 __hrtimer_run_queues+0x52c/0xc60 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline]
 __sysvec_apic_timer_interrupt+0x108/0x410 arch/x86/kernel/apic/apic.c:1056
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0x52/0xc0 arch/x86/kernel/apic/apic.c:1050
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:stack_trace_consume_entry+0x5/0x280 kernel/stacktrace.c:83
Code: f0 5b 41 5e 5d c3 cc cc cc cc cc e8 05 fc cd 09 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 18 48 ba 00 00 00 00 00 fc ff
RSP: 0018:ffffc90000006518 EFLAGS: 00000286
RAX: ffffffff8184f87d RBX: ffffc900000065e0 RCX: 7a67f0fb8b1bf500
RDX: 0000000000000001 RSI: ffffffff8184f87d RDI: ffffc900000065e0
RBP: ffffc900000065b0 R08: ffffc90003387170 R09: 0000000000000000
R10: ffffc90000006578 R11: ffffffff81ac4b00 R12: ffff88802481bc00
R13: 0000000000000000 R14: ffffffff81ac4b00 R15: ffffc90000006528
 arch_stack_walk+0x10d/0x150 arch/x86/kernel/stacktrace.c:27
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2422 [inline]
 slab_free mm/slub.c:4695 [inline]
 kmem_cache_free+0x18f/0x400 mm/slub.c:4797
 skb_ext_del include/linux/skbuff.h:4929 [inline]
 nf_bridge_info_free net/bridge/br_netfilter_hooks.c:156 [inline]
 br_nf_dev_queue_xmit+0x4ee/0x24a0 net/bridge/br_netfilter_hooks.c:851
 NF_HOOK+0x618/0x6b0 include/linux/netfilter.h:318
 br_nf_post_routing+0xb66/0xfe0 net/bridge/br_netfilter_hooks.c:966
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x215/0x3c0 include/linux/netfilter.h:316
 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:-1 [inline]
 br_nf_forward_finish+0xa40/0xe60 net/bridge/br_netfilter_hooks.c:662
 NF_HOOK+0x618/0x6b0 include/linux/netfilter.h:318
 br_nf_forward_ip+0x647/0x7e0 net/bridge/br_netfilter_hooks.c:716
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
 nf_hook include/linux/netfilter.h:273 [inline]
 NF_HOOK+0x215/0x3c0 include/linux/netfilter.h:316
 __br_forward+0x41e/0x600 net/bridge/br_forward.c:115
 br_handle_frame_finish+0x14b4/0x19b0 net/bridge/br_input.c:221
 br_nf_hook_thresh+0x3c3/0x4a0 net/bridge/br_netfilter_hooks.c:-1
 br_nf_pre_routing_finish_ipv6+0x948/0xd00 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:318 [inline]
 br_nf_pre_routing_ipv6+0x37e/0x6b0 net/bridge/br_netfilter_ipv6.c:184
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:283 [inline]
 br_handle_frame+0x982/0x14c0 net/bridge/br_input.c:434
 __netif_receive_skb_core+0x10b6/0x4020 net/core/dev.c:5878
 __netif_receive_skb_one_core net/core/dev.c:5989 [inline]
 __netif_receive_skb+0x72/0x380 net/core/dev.c:6104
 process_backlog+0x60e/0x14f0 net/core/dev.c:6456
 __napi_poll+0xc7/0x360 net/core/dev.c:7506
 napi_poll net/core/dev.c:7569 [inline]
 net_rx_action+0x707/0xe30 net/core/dev.c:7696
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 do_softirq+0xec/0x180 kernel/softirq.c:480
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x17d/0x1c0 kernel/softirq.c:407
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:910 [inline]
 __dev_queue_xmit+0x1d79/0x3b50 net/core/dev.c:4752
 neigh_output include/net/neighbour.h:547 [inline]
 ip6_finish_output2+0x11fb/0x16a0 net/ipv6/ip6_output.c:141
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ndisc_send_skb+0xb54/0x1440 net/ipv6/ndisc.c:512
 ndisc_send_ns+0xcb/0x150 net/ipv6/ndisc.c:670
 addrconf_dad_work+0xaae/0x14b0 net/ipv6/addrconf.c:4282
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g12417 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=3323
rcu: rcu_preempt kthread starved for 10502 jiffies! g12417 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:26632 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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If the report is already addressed, let syzbot know by replying with:
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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.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

^ permalink raw reply	[flat|nested] 4+ messages in thread
* [syzbot] [mm?] INFO: rcu detected stall in sys_munmap (2)
@ 2025-08-22  4:15 syzbot
  2026-08-11 13:11 ` Forwarded: [syz test] net/sched: taprio: reject too-small software schedule intervals syzbot
  0 siblings, 1 reply; 4+ messages in thread
From: syzbot @ 2025-08-22  4:15 UTC (permalink / raw)
  To: Liam.Howlett, akpm, jannh, linux-kernel, linux-mm,
	lorenzo.stoakes, pfalcato, syzkaller-bugs, vbabka

Hello,

syzbot found the following issue on:

HEAD commit:    be48bcf004f9 Merge tag 'for-6.17-rc2-tag' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=136dfba2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=142508fb116c212f
dashboard link: https://syzkaller.appspot.com/bug?extid=8785aaf121cfb2141e0d
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=107a43bc580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/24fd400c6842/disk-be48bcf0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/59146305635d/vmlinux-be48bcf0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b3e5f65cbcc8/bzImage-be48bcf0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8785aaf121cfb2141e0d@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6029/1:b..l P1208/1:b..l P6031/3:b..l P6030/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=6285, q=421 ncpus=2)
task:dhcpcd          state:R  running task     stack:28896 pid:6030  tgid:6030  ppid:5513   task_flags:0x400040 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7288
 irqentry_exit+0x36/0x90 kernel/entry/common.c:197
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:707
RIP: 0010:unwind_next_frame+0xfe7/0x20a0 arch/x86/kernel/unwind_orc.c:664
Code: 85 80 0c 00 00 49 89 6d 40 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e 56 10 00 00 <41> 39 5d 00 0f 84 10 06 00 00 bd 01 00 00 00 e9 de f3 ff ff 48 b8
RSP: 0018:ffffc90003cdf6a8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffc90003ce0000
RDX: 1ffff9200079bee3 RSI: ffffc90003cdfa70 RDI: ffffc90003cdf758
RBP: ffffc90003cdfae0 R08: 0000000000000001 R09: 0000000000000000
R10: ffffc90003cdf718 R11: 00000000000121e6 R12: ffffc90003cdf768
R13: ffffc90003cdf718 R14: ffffc90003cdfa80 R15: ffffc90003cdf74c
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:548
 slab_free_hook mm/slub.c:2378 [inline]
 slab_free mm/slub.c:4680 [inline]
 kmem_cache_free+0x15a/0x4d0 mm/slub.c:4782
 vms_complete_munmap_vmas+0x573/0x970 mm/vma.c:1293
 do_vmi_align_munmap+0x43b/0x7d0 mm/vma.c:1536
 do_vmi_munmap+0x204/0x3e0 mm/vma.c:1584
 __vm_munmap+0x19a/0x390 mm/vma.c:3155
 __do_sys_munmap mm/mmap.c:1080 [inline]
 __se_sys_munmap mm/mmap.c:1077 [inline]
 __x64_sys_munmap+0x59/0x80 mm/mmap.c:1077
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb13ec2f2e7
RSP: 002b:00007fffe10fae78 EFLAGS: 00000206 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 0000562bd1443510 RCX: 00007fb13ec2f2e7
RDX: 0000000000000002 RSI: 0000000000004028 RDI: 00007fb13ea1b000
RBP: 00007fffe10faf80 R08: 0000562bd1432470 R09: 0000000000000001
R10: 00007fffe10fadb0 R11: 0000000000000206 R12: 00007fffe10faea0
R13: 00007fb13ec42000 R14: 0000562bd1443510 R15: 0000000000000000
 </TASK>
task:syz-executor    state:R  running task     stack:27632 pid:6031  tgid:6031  ppid:5870   task_flags:0x400000 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 preempt_schedule_common+0x44/0xc0 kernel/sched/core.c:7145
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 filemap_map_pages+0xe15/0x1670 mm/filemap.c:3791
 do_fault_around mm/memory.c:5531 [inline]
 do_read_fault mm/memory.c:5564 [inline]
 do_fault mm/memory.c:5707 [inline]
 do_pte_missing+0xe39/0x3ba0 mm/memory.c:4234
 handle_pte_fault mm/memory.c:6052 [inline]
 __handle_mm_fault+0x152a/0x2a50 mm/memory.c:6195
 handle_mm_fault+0x589/0xd10 mm/memory.c:6364
 do_user_addr_fault+0x60c/0x1370 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x5c/0xb0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f54cd7177c7
RSP: 002b:00007fffb79a5b40 EFLAGS: 00010246
RAX: 00007f54ce525000 RBX: 0000000000000000 RCX: 0000000000000064
RDX: 00007fffb79a5de9 RSI: 0000000000000002 RDI: 00007fffb79a5dd8
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
R13: 00007fffb79a5c48 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
task:kworker/0:3     state:R  running task     stack:25368 pid:1208  tgid:1208  ppid:2      task_flags:0x4208060 flags:0x00004000
Workqueue: events_power_efficient gc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7288
 irqentry_exit+0x36/0x90 kernel/entry/common.c:197
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:707
RIP: 0010:write_comp_data+0x0/0x90 kernel/kcov.c:240
Code: 48 8b 05 db b4 1a 12 48 8b 80 30 16 00 00 e9 97 05 db 09 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <49> 89 d2 49 89 f8 49 89 f1 65 48 8b 15 a7 b4 1a 12 65 8b 05 b8 b4
RSP: 0018:ffffc9000441fb50 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000040000 RCX: ffffffff89ba2a52
RDX: 0000000000040000 RSI: 0000000000000433 RDI: 0000000000000004
RBP: ffffffff9b2c41ec R08: 0000000000000004 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff9b030610 R12: ffff888031800000
R13: 0000000000000433 R14: dffffc0000000000 R15: 0000000000001770
 gc_worker+0x342/0x16e0 net/netfilter/nf_conntrack_core.c:1549
 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3236
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
task:dhcpcd          state:R  running task     stack:26072 pid:6029  tgid:6029  ppid:5513   task_flags:0x400040 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6961
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7288
 irqentry_exit+0x36/0x90 kernel/entry/common.c:197
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:orc_ip arch/x86/kernel/unwind_orc.c:80 [inline]
RIP: 0010:__orc_find+0x7e/0xf0 arch/x86/kernel/unwind_orc.c:102
Code: ea 3f 48 c1 fe 02 48 01 f2 48 d1 fa 48 8d 5c 95 00 48 89 da 48 c1 ea 03 0f b6 34 0a 48 89 da 83 e2 07 83 c2 03 40 38 f2 7c 05 <40> 84 f6 75 4b 48 63 13 48 01 da 49 39 d5 73 af 4c 8d 63 fc 49 39
RSP: 0018:ffffc90003337648 EFLAGS: 00000202
RAX: ffffffff914e0dd8 RBX: ffffffff90c5215c RCX: dffffc0000000000
RDX: 0000000000000007 RSI: 0000000000000000 RDI: ffffffff90c52148
RBP: ffffffff90c52148 R08: ffffffff914e0e1a R09: 0000000000000000
R10: ffffc900033376f8 R11: 0000000000011271 R12: ffffffff90c52170
R13: ffffffff82127173 R14: ffffffff90c52148 R15: ffffffff90c52148
 orc_find arch/x86/kernel/unwind_orc.c:227 [inline]
 unwind_next_frame+0x2ec/0x20a0 arch/x86/kernel/unwind_orc.c:494
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405
 kmalloc_noprof include/linux/slab.h:905 [inline]
 slab_free_hook mm/slub.c:2369 [inline]
 slab_free mm/slub.c:4680 [inline]
 kmem_cache_free+0x142/0x4d0 mm/slub.c:4782
 vms_complete_munmap_vmas+0x573/0x970 mm/vma.c:1293
 do_vmi_align_munmap+0x43b/0x7d0 mm/vma.c:1536
 do_vmi_munmap+0x204/0x3e0 mm/vma.c:1584
 __vm_munmap+0x19a/0x390 mm/vma.c:3155
 __do_sys_munmap mm/mmap.c:1080 [inline]
 __se_sys_munmap mm/mmap.c:1077 [inline]
 __x64_sys_munmap+0x59/0x80 mm/mmap.c:1077
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb13ec2f2e7
RSP: 002b:00007fffe10fae78 EFLAGS: 00000202 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 0000562bd1443f00 RCX: 00007fb13ec2f2e7
RDX: 0000000000000001 RSI: 000000000002f6d0 RDI: 00007fb13e9c1000
RBP: 00007fffe10faf80 R08: 00000000000004f0 R09: 0000000000000002
R10: 00007fffe10fadb0 R11: 0000000000000202 R12: 00007fffe10faec0
R13: 00007fb13ec42000 R14: 0000562bd1443f00 R15: 0000000000000000
 </TASK>


---
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If the report is already addressed, let syzbot know by replying with:
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^ permalink raw reply	[flat|nested] 4+ messages in thread
* [syzbot] [kernfs?] [mm?] INFO: rcu detected stall in kernfs_fop_open (7)
@ 2025-07-28 23:27 syzbot
  2026-08-11 13:42 ` Forwarded: [syz test] net/sched: taprio: reject too-small software schedule intervals syzbot
  0 siblings, 1 reply; 4+ messages in thread
From: syzbot @ 2025-07-28 23:27 UTC (permalink / raw)
  To: gregkh, linux-kernel, linux-mm, syzkaller-bugs, tj

Hello,

syzbot found the following issue on:

HEAD commit:    25fae0b93d1d Merge tag 'drm-fixes-2025-07-24' of https://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11a5bfd4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a4bcc0a11b3192be
dashboard link: https://syzkaller.appspot.com/bug?extid=19d01f6082ec61dd45b2
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1656bb82580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15a070a2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/26a32daab34b/disk-25fae0b9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/44b0af5dddac/vmlinux-25fae0b9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0687991f0381/bzImage-25fae0b9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+19d01f6082ec61dd45b2@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 ticks this GP) idle=375c/1/0x4000000000000000 softirq=18409/18409 fqs=0
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5512/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=12441, q=623 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5955 Comm: udevd Not tainted 6.16.0-rc7-syzkaller-00034-g25fae0b93d1d #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:hlock_class kernel/locking/lockdep.c:234 [inline]
RIP: 0010:__lock_acquire+0xa4f/0xd20 kernel/locking/lockdep.c:5237
Code: e5 ff 90 0f 0b 90 90 90 31 c0 48 8b 3c 24 48 83 78 40 00 0f 84 8c 02 00 00 41 8b 46 20 25 ff 1f 00 00 48 0f a3 05 f1 3a 09 12 <73> 10 48 69 c0 c8 00 00 00 48 8d 80 f0 82 48 93 eb 40 83 3d 38 ca
RSP: 0018:ffffc90000007b70 EFLAGS: 00000003
RAX: 000000000000006d RBX: 0000000000000001 RCX: 00000000ab2b819a
RDX: 00000000001bf57d RSI: 00000000f5f6d907 RDI: ffff888061b90000
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff81ae7962
R10: dffffc0000000000 R11: fffffbfff1f43b9f R12: 000000000000006e
R13: ffff888061b90af0 R14: ffff888061b90b18 R15: 4d4df099ab2b819a
FS:  00007fe3e1610880(0000) GS:ffff888125c23000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f509ec85f98 CR3: 0000000032c5c000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
 _raw_spin_lock_irq+0xa2/0xf0 kernel/locking/spinlock.c:170
 __run_hrtimer kernel/time/hrtimer.c:1765 [inline]
 __hrtimer_run_queues+0x602/0xc60 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline]
 __sysvec_apic_timer_interrupt+0x108/0x410 arch/x86/kernel/apic/apic.c:1056
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1050
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:26 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:109 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:127 [inline]
RIP: 0010:lock_acquire+0xc9/0x360 kernel/locking/lockdep.c:5867
Code: 01 11 85 c0 0f 85 eb 00 00 00 65 48 8b 04 25 08 d0 9f 92 83 b8 ec 0a 00 00 00 0f 85 d5 00 00 00 48 c7 44 24 30 00 00 00 00 9c <8f> 44 24 30 4c 89 74 24 10 4d 89 fe 4c 8b 7c 24 30 fa 48 c7 c7 20
RSP: 0018:ffffc90003197290 EFLAGS: 00000246
RAX: ffff888061b90000 RBX: 0000000000000000 RCX: 0d0c881f9d5e1900
RDX: 0000000000000000 RSI: ffffffff8172ab02 RDI: 1ffffffff1c27e1c
RBP: ffffffff8172aae5 R08: 0000000000000000 R09: 0000000000000000
R10: ffffc90003197458 R11: ffffffff81acfe40 R12: 0000000000000002
R13: ffffffff8e13f0e0 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:841 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1155 [inline]
 unwind_next_frame+0xc2/0x2390 arch/x86/kernel/unwind_orc.c:479
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __kmalloc_cache_noprof+0x230/0x3d0 mm/slub.c:4359
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 kernfs_fop_open+0x397/0xca0 fs/kernfs/file.c:623
 do_dentry_open+0xdf0/0x1970 fs/open.c:964
 vfs_open+0x3b/0x340 fs/open.c:1094
 do_open fs/namei.c:3896 [inline]
 path_openat+0x2ee5/0x3830 fs/namei.c:4055
 do_filp_open+0x1fa/0x410 fs/namei.c:4082
 do_sys_openat2+0x121/0x1c0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe3e0ea7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffe447dd8f0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fe3e1610880 RCX: 00007fe3e0ea7407
RDX: 0000000000080000 RSI: 00007ffe447dda70 RDI: ffffffffffffff9c
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000556b9eca17f5
R13: 0000556b9eca17f5 R14: 0000000000000001 R15: 0000556b9ecbc140
 </TASK>
task:dhcpcd          state:R  running task     stack:21384 pid:5512  tgid:5512  ppid:5511   task_flags:0x400140 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:6966
 preempt_schedule+0xae/0xc0 kernel/sched/core.c:6990
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0xfd/0x110 kernel/locking/spinlock.c:194
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 __wake_up_common_lock+0x190/0x1f0 kernel/sched/wait.c:108
 sock_def_readable+0x1fb/0x550 net/core/sock.c:3583
 unix_dgram_sendmsg+0xd78/0x17d0 net/unix/af_unix.c:2236
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:727
 sock_write_iter+0x258/0x330 net/socket.c:1131
 do_iter_readv_writev+0x56b/0x7f0 fs/read_write.c:-1
 vfs_writev+0x31a/0x960 fs/read_write.c:1057
 do_writev+0x14d/0x2d0 fs/read_write.c:1103
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f810cb46407
RSP: 002b:00007ffd0761b7f0 EFLAGS: 00000202 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f810cabc740 RCX: 00007f810cb46407
RDX: 0000000000000002 RSI: 00007ffd0761b890 RDI: 000000000000000b
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000b
R13: 00007f810cabc6c8 R14: 0000000000000000 R15: 00007ffd0762b9a0
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g12441 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=4027
rcu: rcu_preempt kthread starved for 10502 jiffies! g12441 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27128 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x16fd/0x4cf0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6879
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2054
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2256
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-08-11 13:43 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-01-13 18:06 [syzbot] [bridge?] INFO: rcu detected stall in br_handle_frame (6) syzbot
2026-08-11 13:43 ` Forwarded: [syz test] net/sched: taprio: reject too-small software schedule intervals syzbot
  -- strict thread matches above, loose matches on Subject: below --
2025-08-22  4:15 [syzbot] [mm?] INFO: rcu detected stall in sys_munmap (2) syzbot
2026-08-11 13:11 ` Forwarded: [syz test] net/sched: taprio: reject too-small software schedule intervals syzbot
2025-07-28 23:27 [syzbot] [kernfs?] [mm?] INFO: rcu detected stall in kernfs_fop_open (7) syzbot
2026-08-11 13:42 ` Forwarded: [syz test] net/sched: taprio: reject too-small software schedule intervals syzbot

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