syzbot


INFO: rcu detected stall in sys_munmap

Status: upstream: reported on 2025/07/12 12:20
Reported-by: syzbot+9358c7457a4eb85a257e@syzkaller.appspotmail.com
First crash: 102d, last: 18d
Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_munmap kasan mm 1 1 777d 777d 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 98d 98d 0/3 upstream: reported on 2025/07/16 12:55
linux-6.1 INFO: rcu detected stall in sys_munmap (2) 1 10 1d23h 204d 0/3 upstream: reported on 2025/04/02 07:15
upstream INFO: rcu detected stall in sys_munmap (2) mm 1 syz 26 42d 62d 0/29 upstream: reported syz repro on 2025/08/22 04:15
linux-6.1 INFO: rcu detected stall in sys_munmap 1 1 457d 457d 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): P5796/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=17817, q=220 ncpus=2)
task:udevd           state:R  running task     stack:24808 pid:5796  ppid:5159   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 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:arch_atomic_inc include/linux/instrumented.h:96 [inline]
RIP: 0010:raw_atomic_inc include/linux/atomic/atomic-arch-fallback.h:979 [inline]
RIP: 0010:atomic_inc include/linux/atomic/atomic-instrumented.h:436 [inline]
RIP: 0010:mas_validate_parent_slot lib/maple_tree.c:7044 [inline]
RIP: 0010:mt_validate+0x858/0x4530 lib/maple_tree.c:7228
Code: 3b ac 24 38 01 00 00 0f 85 a2 00 00 00 e8 b0 85 29 f7 48 c7 c7 a0 f5 2b 97 be 04 00 00 00 e8 2f df 80 f7 f0 ff 05 48 f0 cf 0c <eb> 0e 4d 39 e5 0f 84 f6 00 00 00 e8 88 85 29 f7 48 39 5c 24 38 0f
RSP: 0018:ffffc9000458f820 EFLAGS: 00000203
RAX: ffffffff8a5c0501 RBX: 0000000000000005 RCX: ffffffff8a5c0551
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffffff972bf5a0
RBP: ffffc9000458f9f0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffffbfff2e57eb4 R12: ffff88801bf4a40c
R13: ffff88801bf4a40c R14: 0000000000000005 R15: ffff88802dacbc78
 validate_mm+0xb1/0x420 mm/mmap.c:288
 do_vmi_align_munmap+0x148a/0x1660 mm/mmap.c:2597
 do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2660
 __vm_munmap+0x193/0x3c0 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:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f955231e097
RSP: 002b:00007fff5b6efd78 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 00005651df9e76e0 RCX: 00007f955231e097
RDX: 00005651df9efb68 RSI: 0000000000000200 RDI: 00007f9552988000
RBP: 0000000000000001 R08: 00005651df9f4ca0 R09: 00005651df9e16a0
R10: 0000000000000000 R11: 0000000000000246 R12: 00005651df9df0b0
R13: 00007f9552ab039c R14: 0000000000000200 R15: 0000000000000009
 </TASK>
rcu: rcu_preempt kthread starved for 9781 jiffies! g17817 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:27752 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 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: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:148
Code: 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 93 c8 39 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c6
RAX: cb539a9fe58c4600 RBX: ffffffff816185ab RCX: cb539a9fe58c4600
RDX: 0000000000000001 RSI: ffffffff8aaabce0 RDI: ffffffff8afc63c0
RBP: ffffc90000187f20 R08: ffff8880b8f36b2b R09: 1ffff110171e6d65
R10: dffffc0000000000 R11: ffffed10171e6d66 R12: ffffffff8e4a82e8
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff1100364e780
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2e912ff8 CR3: 0000000060a58000 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:170 [inline]
 do_idle+0x1eb/0x510 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/04 19:31 linux-6.6.y f34f16e5c632 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_munmap
2025/09/10 07:49 linux-6.6.y fe9731e10004 fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_munmap
2025/08/17 07:59 linux-6.6.y bb9c90ab9c5a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_munmap
2025/07/12 12:20 linux-6.6.y 59a2de10b81a 3cda49cf .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.