syzbot

 sign-in | mailing list | source | docs
🐞 Open [860]
🐞 Fixed [141]
🐞 Invalid [980]
⬇ Missing Backports [74]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

INFO: rcu detected stall in brk

Status: upstream: reported on 2025/12/31 20:11
Reported-by: syzbot+0b349cf367fce0d6eb59@syzkaller.appspotmail.com
First crash: 11d, last: 11d
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in brk mm 1 1 631d 631d 0/29 auto-obsoleted due to no activity on 2024/07/20 02:57
upstream INFO: rcu detected stall in brk (2) mm 1 syz 2 375d 437d 0/29 upstream: reported syz repro on 2024/10/31 16:03
upstream INFO: rcu detected stall in sys_brk mm 1 1 721d 721d 0/29 auto-obsoleted due to no activity on 2024/04/21 01:31
linux-6.1 INFO: rcu detected stall in sys_brk 1 1 585d 585d 0/3 auto-obsoleted due to no activity on 2024/09/13 10:58

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6139/1:b..l P6133/1:b..l
	(detected by 0, t=10502 jiffies, g=23437, q=255 ncpus=2)
task:syz.3.394       state:R  running task     stack:24512 pid:6133  ppid:4267   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6730
 preempt_schedule+0xa7/0xb0 kernel/sched/core.c:6754
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 unwind_next_frame+0x1892/0x20b0 arch/x86/kernel/unwind_orc.c:629
 arch_stack_walk+0x10c/0x140 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
 save_stack+0xf3/0x1e0 mm/page_owner.c:127
 __reset_page_owner+0x51/0x1a0 mm/page_owner.c:148
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page_list+0xbb/0x8e0 mm/page_alloc.c:3525
 release_pages+0x1f92/0x2200 mm/swap.c:1035
 __pagevec_release+0x6d/0xe0 mm/swap.c:1055
 pagevec_release include/linux/pagevec.h:71 [inline]
 folio_batch_release include/linux/pagevec.h:135 [inline]
 shmem_undo_range+0x75b/0x2050 mm/shmem.c:946
 shmem_truncate_range mm/shmem.c:1062 [inline]
 shmem_evict_inode+0x248/0xa40 mm/shmem.c:1171
 evict+0x485/0x870 fs/inode.c:705
 __dentry_kill+0x431/0x650 fs/dcache.c:611
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xfa/0x1d0 fs/dcache.c:918
 __fput+0x5e0/0x920 fs/file_table.c:328
 task_work_run+0x1ca/0x250 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0x93e/0x2400 kernel/exit.c:880
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 get_signal+0x1272/0x1350 kernel/signal.c:2871
 arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f7a0c78f749
RSP: 002b:00007f7a0d5f2038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: 0000000000000064 RBX: 00007f7a0c9e5fa0 RCX: 00007f7a0c78f749
RDX: 0000000000000000 RSI: 0000200000000100 RDI: 0000000000000006
RBP: 00007f7a0c813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a0c9e6038 R14: 00007f7a0c9e5fa0 R15: 00007ffcef42e628
 </TASK>
task:modprobe        state:R  running task     stack:24352 pid:6139  ppid:51     flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6873
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:mt_slot lib/maple_tree.c:816 [inline]
RIP: 0010:mas_slot lib/maple_tree.c:849 [inline]
RIP: 0010:mas_get_slot lib/maple_tree.c:6680 [inline]
RIP: 0010:mas_validate_gaps lib/maple_tree.c:6978 [inline]
RIP: 0010:mt_validate+0x2ca1/0x4c90 lib/maple_tree.c:7246
Code: 00 49 01 c5 4c 8b b4 24 20 01 00 00 48 8b 44 24 20 4a 8d 3c 28 48 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 <74> 05 e8 68 dc d2 f7 48 8b 44 24 20 49 8b 44 05 00 48 89 44 24 68
RSP: 0018:ffffc90003c67900 EFLAGS: 00000246
RAX: 1ffff11004fd3bd2 RBX: ffffffff8b910828 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff888027e9de90
RBP: ffffc90003c67ad0 R08: ffff88807e525940 R09: 0000000000000004
R10: 0000000000000003 R11: 0000000000000000 R12: 00007f1dd07bbfff
R13: ffff888027e9de80 R14: ffff888076e30000 R15: 0000000000000002
 validate_mm_mt+0xcd/0x420 mm/mmap.c:295
 validate_mm+0xcc/0x2b0 mm/mmap.c:332
 do_brk_flags+0x6ba/0xb80 mm/mmap.c:3160
 __do_sys_brk mm/mmap.c:262 [inline]
 __se_sys_brk+0x8af/0x9e0 mm/mmap.c:170
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1dd09196c7
RSP: 002b:00007ffee8bd6418 EFLAGS: 00000206 ORIG_RAX: 000000000000000c
RAX: ffffffffffffffda RBX: 0000557c62ad5000 RCX: 00007f1dd09196c7
RDX: 00007f1dd09fbe50 RSI: 00007f1dd09f4ac0 RDI: 0000557c62ad5000
RBP: 0000557c62ab4000 R08: 0000000000021000 R09: 0000000000000000
R10: 00007f1dd09f4ac0 R11: 0000000000000206 R12: 00007f1dd09fbe50
R13: 00007f1dd09f4b20 R14: 0000000000001000 R15: 00000000000002b0
 </TASK>
rcu: rcu_preempt kthread starved for 10577 jiffies! g23437 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:27400 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </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: 6152 Comm: syz.0.398 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:lockdep_recursion_finish kernel/locking/lockdep.c:467 [inline]
RIP: 0010:lock_acquire+0x1d1/0x490 kernel/locking/lockdep.c:5664
Code: 00 ff 75 10 ff 74 24 30 e8 1c 04 00 00 48 83 c4 20 48 c7 c7 80 17 6c 8a e8 fc 7e ad 08 b8 ff ff ff ff 65 0f c1 05 1f 76 9f 7e <83> f8 01 0f 85 f9 00 00 00 48 c7 84 24 80 00 00 00 00 00 00 00 9c
RSP: 0018:ffffc900001e0c40 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000000 RCX: cceedc6cb57a9300
RDX: 0000000000000000 RSI: ffffffff8a6c1780 RDI: ffffffff8abef920
RBP: ffffc900001e0d48 R08: dffffc0000000000 R09: fffffbfff211904a
R10: fffffbfff211904a R11: 1ffffffff2119049 R12: 0000000000000001
R13: 1ffff9200003c194 R14: 0000000000000046 R15: dffffc0000000000
FS:  00007f4863fed6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32493a CR3: 0000000066654000 CR4: 00000000003506e0
DR0: 0000000000000008 DR1: 0000000000000002 DR2: 0000000000000081
DR3: ffffffffefffff15 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 seqcount_lockdep_reader_access+0xc6/0x1c0 include/linux/seqlock.h:102
 timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
 ktime_get+0x7b/0x270 kernel/time/timekeeping.c:848
 clockevents_program_event+0xe2/0x310 kernel/time/clockevents.c:326
 hrtimer_interrupt+0x59d/0x9c0 kernel/time/hrtimer.c:1886
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202
Code: f5 ff 0f 1f 00 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ae 05 49 f7 48 89 df e8 06 cb 49 f7 e8 d1 bd 6c f7 fb bf 01 00 00 00 <e8> 96 43 3d f7 65 8b 05 27 f1 e7 75 85 c0 74 02 5b c3 e8 c4 02 e6
RSP: 0018:ffffc90003fc7b98 EFLAGS: 00000282
RAX: cceedc6cb57a9300 RBX: ffff8880597cd340 RCX: cceedc6cb57a9300
RDX: dffffc0000000000 RSI: ffffffff8a6c0600 RDI: 0000000000000001
RBP: ffff8880597cd5d8 R08: dffffc0000000000 R09: ffffed100b2f9a69
R10: ffffed100b2f9a69 R11: 1ffff1100b2f9a68 R12: 1ffff1100b2f9abb
R13: 0000000000000011 R14: dffffc0000000000 R15: 0000000000000000
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 get_signal+0x1163/0x1350 kernel/signal.c:2874
 arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f486318f749
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:00007f4863fed0e8 EFLAGS: 00000246
RAX: fffffffffffffffc RBX: 00007f48633e6098 RCX: 00007f486318f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f48633e6098
RBP: 00007f48633e6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f48633e6128 R14: 00007ffe42b73ce0 R15: 00007ffe42b73dc8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/31 20:10 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in brk
* Struck through repros no longer work on HEAD.