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INFO: rcu detected stall in sys_munmap (2)

Status: upstream: reported on 2026/05/11 10:40
Reported-by: syzbot+4805acafe4af1e1be281@syzkaller.appspotmail.com
First crash: 3d20h, last: 3d20h
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in sys_munmap 1 7 135d 306d 0/2 auto-obsoleted due to no activity on 2026/04/09 22:56
upstream INFO: rcu detected stall in sys_munmap mm kasan 1 1 981d 981d 0/29 auto-obsoleted due to no activity on 2023/11/06 05:09
linux-5.15 INFO: rcu detected stall in sys_munmap 1 1 302d 302d 0/3 auto-obsoleted due to no activity on 2025/10/24 12:55
linux-6.1 INFO: rcu detected stall in sys_munmap (2) origin:upstream 1 C error 23 16d 407d 0/3 upstream: reported C repro on 2025/04/02 07:15
upstream INFO: rcu detected stall in sys_munmap (2) mm 1 C error error 43 17d 266d 0/29 upstream: reported C repro on 2025/08/22 04:15
linux-6.1 INFO: rcu detected stall in sys_munmap 1 1 661d 661d 0/3 auto-obsoleted due to no activity on 2024/10/31 01:03

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P1307/1:b..l P5794/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=12349, q=719 ncpus=2)
task:udevd           state:R  running task     stack:23048 pid:5794  ppid:5141   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 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:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:244 [inline]
RIP: 0010:__sanitizer_cov_trace_cmp8+0x8/0x80 kernel/kcov.c:293
Code: 08 04 00 00 00 48 89 7c 11 10 48 89 74 11 18 48 89 44 11 20 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0d a0 91 7c 7e 65 8b 15 a1 91 7c 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc9000448f838 EFLAGS: 00000246
RAX: ffffffff8a73e846 RBX: ffff88802d04c400 RCX: dffffc0000000000
RDX: ffff88807b219e00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000448f9f0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff2edb9ec R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000003
 mas_validate_gaps lib/maple_tree.c:7013 [inline]
 mt_validate+0x2f86/0x4400 lib/maple_tree.c:7234
 validate_mm+0xc6/0x450 mm/mmap.c:288
 do_vmi_align_munmap+0x14ff/0x16d0 mm/mmap.c:2597
 do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2660
 __vm_munmap+0x1a2/0x3c0 mm/mmap.c:2961
 __do_sys_munmap mm/mmap.c:2978 [inline]
 __se_sys_munmap mm/mmap.c:2975 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:2975
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd52b31e097
RSP: 002b:00007fffcf972788 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 000055864fa9a630 RCX: 00007fd52b31e097
RDX: 000055864fa9a648 RSI: 0000000000000200 RDI: 00007fd52ba84000
RBP: 000055864fa86050 R08: 0000000000000000 R09: 0000000000000000
R10: 000055864fa860b0 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 000055864fa9a648 R15: 00007fd52bbac39c
 </TASK>
task:kworker/u4:6    state:R  running task     stack:23016 pid:1307  ppid:2      flags:0x00004000
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 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:lockdep_enabled kernel/locking/lockdep.c:122 [inline]
RIP: 0010:lock_acquire+0x10a/0x420 kernel/locking/lockdep.c:5730
Code: 0f 85 1d 02 00 00 83 3d 4f 23 23 0d 00 0f 84 0c 01 00 00 65 8b 05 be 5e 9a 7e 85 c0 0f 85 44 01 00 00 65 4c 8b 35 86 8a 9b 7e <49> 81 c6 dc 0a 00 00 4c 89 f0 48 c1 e8 03 42 0f b6 04 38 84 c0 0f
RSP: 0018:ffffc90004effa40 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 20794425131f4200
RDX: 0000000000000000 RSI: ffffffff8b1c8f80 RDI: ffffffff8b1c8f40
RBP: ffffc90004effb48 R08: ffffffff8e8b19af R09: 1ffffffff1d16335
R10: dffffc0000000000 R11: fffffbfff1d16336 R12: 1ffff920009dff54
R13: ffffffff8d1320e0 R14: ffff888025000000 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
 batadv_nc_worker+0xef/0x610 net/batman-adv/network-coding.c:719
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
 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: rcu_preempt kthread starved for 9932 jiffies! g12349 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:27672 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 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:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: 19 21 02 c3 cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d e3 d3 41 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2e 41 89 de 80
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c6
RAX: 3b47095ba919fa00 RBX: ffffffff8162a8f1 RCX: 3b47095ba919fa00
RDX: 0000000000000001 RSI: ffffffff8acac9e0 RDI: ffffffff8b1c8fa0
RBP: ffffc90000187f20 R08: ffff8880b8f36b2b R09: 1ffff110171e6d65
R10: dffffc0000000000 R11: ffffed10171e6d66 R12: 1ffff92000030fc8
R13: dffffc0000000000 R14: 1ffff11003848780 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2de15ff8 CR3: 000000002e9c2000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:178 [inline]
 do_idle+0x221/0x590 kernel/sched/idle.c:302
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:401
 start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/11 10:40 linux-6.6.y 3b9f64db0496 845acb1c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_munmap
* Struck through repros no longer work on HEAD.