syzbot


INFO: rcu detected stall in sys_pipe2

Status: upstream: reported on 2025/12/05 08:23
Reported-by: syzbot+975ce165412796899fa4@syzkaller.appspotmail.com
First crash: 56d, last: 15d
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_pipe2 (2) mm 1 syz done done 111 7d23h 445d 0/29 upstream: reported syz repro on 2024/11/10 15:52
upstream INFO: rcu detected stall in sys_pipe2 fs 1 1 1563d 1563d 0/29 auto-closed as invalid on 2022/01/17 19:05

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5773/1:b..l P5757/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=13717, q=333 ncpus=2)
task:syz-executor    state:R  running task     stack:22544 pid:5757  ppid:5756   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x1f2/0x410 kernel/locking/lockdep.c:5758
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f5 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 66 43 c7 44 3c 09 00 00 43 c6 44 3c 0b 00
RSP: 0018:ffffc9000462f840 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: e5b6d4ca79f26100
RDX: 0000000000000000 RSI: ffffffff8aaace60 RDI: ffffffff8afc73a0
RBP: ffffc9000462f948 R08: dffffc0000000000 R09: 1ffffffff21b2ca0
R10: dffffc0000000000 R11: fffffbfff21b2ca1 R12: 1ffff920008c5f14
R13: ffffffff8cd2ffa0 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 page_ext_get+0x3e/0x2b0 mm/page_ext.c:508
 __reset_page_owner+0x2e/0x190 mm/page_owner.c:145
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x31d/0x410 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3519
 kmem_cache_zalloc include/linux/slab.h:711 [inline]
 alloc_empty_file+0x9e/0x1d0 fs/file_table.c:206
 alloc_file+0x5c/0x600 fs/file_table.c:293
 alloc_file_clone+0x2a/0xb0 fs/file_table.c:348
 create_pipe_files+0x420/0x700 fs/pipe.c:946
 __do_pipe_flags+0x4c/0x2c0 fs/pipe.c:968
 do_pipe2+0x9d/0x170 fs/pipe.c:1019
 __do_sys_pipe2 fs/pipe.c:1037 [inline]
 __se_sys_pipe2 fs/pipe.c:1035 [inline]
 __x64_sys_pipe2+0x5a/0x70 fs/pipe.c:1035
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f040dd8e469
RSP: 002b:00007fff5b0dba68 EFLAGS: 00000246 ORIG_RAX: 0000000000000125
RAX: ffffffffffffffda RBX: 000055558fc04430 RCX: 00007f040dd8e469
RDX: 0000000000000004 RSI: 0000000000000000 RDI: 00007fff5b0dba78
RBP: 000055558fc04430 R08: 0000000000000007 R09: 000055558fc03e10
R10: 178b71c865fbd38c R11: 0000000000000246 R12: 000055558fc07ae0
R13: 000055558fc09d48 R14: 000055558fc08188 R15: 00007fff5b0dbba0
 </TASK>
task:syz-executor    state:R  running task     stack:21640 pid:5773  ppid:5765   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 preempt_schedule_notrace+0xce/0x110 kernel/sched/core.c:6960
 preempt_schedule_notrace_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:46
 rcu_is_watching+0x7a/0xb0 kernel/rcu/tree.c:701
 rcu_read_lock_held_common kernel/rcu/update.c:108 [inline]
 rcu_read_lock_held+0x15/0x40 kernel/rcu/update.c:348
 lookup_page_ext mm/page_ext.c:240 [inline]
 page_ext_get+0x193/0x2b0 mm/page_ext.c:509
 __page_table_check_zero+0x138/0x4b0 mm/page_table_check.c:148
 page_table_check_free include/linux/page_table_check.h:41 [inline]
 free_pages_prepare mm/page_alloc.c:1155 [inline]
 free_unref_page_prepare+0x7e1/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x31d/0x410 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 ____kasan_kmalloc mm/kasan/common.c:341 [inline]
 __kasan_kmalloc+0x22/0xa0 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc+0xb4/0x240 mm/slab_common.c:1020
 kmalloc include/linux/slab.h:604 [inline]
 tomoyo_realpath_from_path+0xe3/0x5d0 security/tomoyo/realpath.c:251
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x20f/0x4b0 security/tomoyo/file.c:822
 security_inode_getattr+0xd3/0x120 security/security.c:2153
 vfs_getattr fs/stat.c:173 [inline]
 vfs_fstat fs/stat.c:198 [inline]
 vfs_fstatat+0xc9/0x1b0 fs/stat.c:295
 __do_sys_newfstatat fs/stat.c:463 [inline]
 __se_sys_newfstatat fs/stat.c:457 [inline]
 __x64_sys_newfstatat+0x117/0x190 fs/stat.c:457
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f46fed8de3a
RSP: 002b:00007ffc97298b08 EFLAGS: 00000206 ORIG_RAX: 0000000000000106
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f46fed8de3a
RDX: 00007ffc97298b10 RSI: 00007f46fee50f82 RDI: 0000000000000003
RBP: 00007ffc97298b10 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000206 R12: 00007ffc97299d10
R13: 00007f46fee13d7d R14: 000000000001d5ae R15: 00007ffc97299d50
 </TASK>
rcu: rcu_preempt kthread starved for 5041 jiffies! g13717 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:26728 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 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>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3380 Comm: kworker/R-bat_e Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: bat_events batadv_tt_purge
RIP: 0010:ebt_do_table+0x206/0x2750 net/bridge/netfilter/ebtables.c:220
Code: 3c 08 00 74 08 4c 89 ff e8 f7 69 8c f8 4d 8b 27 4d 8d 74 24 2c 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 <84> c0 0f 85 07 25 00 00 41 8b 06 89 44 24 4c 4c 89 64 24 08 4c 89
RSP: 0018:ffffc900001f0560 EFLAGS: 00000a07
RAX: 0000000000000000 RBX: ffffc90002f92000 RCX: dffffc0000000000
RDX: 0000000000000100 RSI: 0000000000000005 RDI: 0000000000000006
RBP: ffffc900001f0710 R08: ffff888143bc3c43 R09: 1ffff11028778788
R10: dffffc0000000000 R11: ffffed1028778789 R12: ffffc90002f94000
R13: 000000000000003f R14: ffffc90002f9402c R15: ffffc90002f92030
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe4350ce40 CR3: 000000002f055000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 ebt_broute+0x1f0/0x760 net/bridge/netfilter/ebtable_broute.c:61
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
 br_handle_frame+0x957/0x14c0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xf6b/0x3ac0 net/core/dev.c:5532
 __netif_receive_skb_one_core net/core/dev.c:5636 [inline]
 __netif_receive_skb+0x74/0x290 net/core/dev.c:5752
 process_backlog+0x385/0x6f0 net/core/dev.c:6080
 __napi_poll+0xc0/0x460 net/core/dev.c:6642
 napi_poll net/core/dev.c:6709 [inline]
 net_rx_action+0x5ea/0xc00 net/core/dev.c:6846
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 do_softirq+0xed/0x180 kernel/softirq.c:479
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x178/0x1c0 kernel/softirq.c:406
 spin_unlock_bh include/linux/spinlock.h:396 [inline]
 batadv_tt_local_purge+0x2a7/0x340 net/batman-adv/translation-table.c:1371
 batadv_tt_purge+0x35/0x9f0 net/batman-adv/translation-table.c:3582
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 rescuer_thread+0x50b/0xbe0 kernel/workqueue.c:2888
 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>
net_ratelimit: 12641 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ee:45:9d:ff:44:e9, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ee:45:9d:ff:44:e9, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ee:45:9d:ff:44:e9, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ee:45:9d:ff:44:e9, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ee:45:9d:ff:44:e9, vlan:0)

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/14 18:54 linux-6.6.y c596736dadab d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_pipe2
2025/12/22 02:27 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_pipe2
2025/12/05 08:22 linux-6.6.y 4791134e4aeb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_pipe2
* Struck through repros no longer work on HEAD.