syzbot


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: 40d, last: 1d13h
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 172d 343d 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 1018d 1018d 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 339d 339d 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 26 now 445d 0/3 upstream: reported C repro on 2025/04/02 07:15
upstream INFO: rcu detected stall in sys_munmap (2) mm prio:low 1 C error error 44 15d 303d 0/29 upstream: reported C repro on 2025/08/22 04:15
linux-6.1 INFO: rcu detected stall in sys_munmap 1 1 698d 698d 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): P11422/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=53445, q=228 ncpus=2)
task:udevd           state:R  running task     stack:25032 pid:11422 ppid:5142   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 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:mte_parent_slot lib/maple_tree.c:530 [inline]
RIP: 0010:mas_validate_gaps lib/maple_tree.c:7010 [inline]
RIP: 0010:mt_validate+0x2e53/0x4410 lib/maple_tree.c:7234
Code: 83 e6 02 31 ff e8 cd 85 15 f7 4c 89 f0 48 83 e0 02 0f 84 d0 0a 00 00 b9 03 00 00 00 41 81 e6 fc 00 00 00 49 d3 ee 4c 89 34 24 <eb> 17 e8 66 81 15 f7 e9 68 01 00 00 e8 5c 81 15 f7 48 c7 04 24 00
RSP: 0018:ffffc90012df7860 EFLAGS: 00000207
RAX: 0000000000000002 RBX: ffff88807447aa1e RCX: 0000000000000003
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffffc90012df7a10 R08: ffff88802d518000 R09: 0000000000000003
R10: 0000000000000002 R11: 0000000000000000 R12: 1ffff11004368700
R13: dffffc0000000000 R14: 0000000000000003 R15: ffffffff8be9d441
 validate_mm+0xc6/0x450 mm/mmap.c:288
 do_vmi_align_munmap+0x14dd/0x16a0 mm/mmap.c:2597
 do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2660
 __vm_munmap+0x19e/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+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb1a071e097
RSP: 002b:00007fff685aa398 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 000055af743d1e00 RCX: 00007fb1a071e097
RDX: 000055af743d91d8 RSI: 0000000000000200 RDI: 00007fb1a0e29000
RBP: 0000000000000004 R08: 0000000000000030 R09: 000055af743d53d0
R10: 0000000000000000 R11: 0000000000000246 R12: 000055af743ca0b0
R13: 00007fb1a0f5639c R14: 0000000000000800 R15: 0000000000000009
 </TASK>
rcu: rcu_preempt kthread starved for 10513 jiffies! g53445 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:27848 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 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+0x30d/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 05/09/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: dc 23 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 43 67 44 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2c 89 cb 80 f9
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c6
RAX: 62e8c39d119a7800 RBX: ffffffff81628c14 RCX: 62e8c39d119a7800
RDX: 0000000000000001 RSI: ffffffff8acacb60 RDI: ffffffff8b1c7be0
RBP: ffffc90000187f20 R08: ffff8880b8f36bab R09: 1ffff110171e6d75
R10: dffffc0000000000 R11: ffffed10171e6d76 R12: 1ffff92000030fc8
R13: dffffc0000000000 R14: 1ffff110036cd780 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d98bf96168 CR3: 000000000cf32000 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+0x334/0x5c0 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 (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/19 18:50 linux-6.6.y d1cfde2d5d15 570c59ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_munmap
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.