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: 52d, last: 16d
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 726d 726d 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 48d 48d 0/3 upstream: reported on 2025/07/16 12:55
linux-6.1 INFO: rcu detected stall in sys_munmap (2) 1 7 19d 153d 0/3 upstream: reported on 2025/04/02 07:15
upstream INFO: rcu detected stall in sys_munmap (2) mm 1 syz 24 14d 11d 0/29 upstream: reported syz repro on 2025/08/22 04:15
linux-6.1 INFO: rcu detected stall in sys_munmap 1 1 406d 406d 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): P5910/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=15249, q=473 ncpus=2)
task:udevd           state:R  running task     stack:23400 pid:5910  ppid:5157   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:mt_locked lib/maple_tree.c:805 [inline]
RIP: 0010:mt_slot lib/maple_tree.c:812 [inline]
RIP: 0010:mas_slot lib/maple_tree.c:845 [inline]
RIP: 0010:mt_validate_nulls lib/maple_tree.c:7181 [inline]
RIP: 0010:mt_validate+0x3f15/0x4530 lib/maple_tree.c:7235
Code: 00 03 00 00 44 89 fe e8 d9 72 2a f7 41 81 ff 00 03 00 00 75 35 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 <74> 08 4c 89 f7 e8 31 b6 81 f7 4d 8b 36 4d 85 f6 74 5d e8 f4 6e 2a
RSP: 0018:ffffc900050376c0 EFLAGS: 00000246
RAX: 1ffff11004fc8d18 RBX: ffff888075c21800 RCX: dffffc0000000000
RDX: ffff88802876bc00 RSI: 0000000000000300 RDI: 0000000000000300
RBP: ffffc90005037890 R08: ffff88802876bc00 R09: 0000000000000003
R10: 0000000000000003 R11: 0000000000000000 R12: ffff8880766ae000
R13: ffff88802ea3cc80 R14: ffff888027e468c0 R15: 0000000000000300
 validate_mm+0xb1/0x420 mm/mmap.c:287
 __split_vma+0xa93/0xc00 mm/mmap.c:2421
 do_vmi_align_munmap+0x377/0x1660 mm/mmap.c:2510
 do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2656
 __vm_munmap+0x193/0x3c0 mm/mmap.c:2957
 __do_sys_munmap mm/mmap.c:2974 [inline]
 __se_sys_munmap mm/mmap.c:2971 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:2971
 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: 0033:0x7f493511e097
RSP: 002b:00007ffde5618868 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 000055a1283196a0 RCX: 00007f493511e097
RDX: 000055a1283267c8 RSI: 0000000000000200 RDI: 00007f493574d000
RBP: 0000000000000001 R08: 000055a128323900 R09: 000055a12832fd80
R10: 0000000000000000 R11: 0000000000000246 R12: 000055a128333720
R13: 00007f493589c39c R14: 0000000000000200 R15: 0000000000000009
 </TASK>
rcu: rcu_preempt kthread starved for 10213 jiffies! g15249 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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: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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.6.102-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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 e3 e6 3a 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:ffffffff8ca07d80 EFLAGS: 000002c6
RAX: 14bd406696343200 RBX: ffffffff8161914b RCX: 14bd406696343200
RDX: 0000000000000001 RSI: ffffffff8aaab9c0 RDI: ffffffff8afc66c0
RBP: ffffffff8ca07eb8 R08: ffff8880b8e36d4b R09: 1ffff110171c6da9
R10: dffffc0000000000 R11: ffffed10171c6daa R12: ffffffff8e4a8828
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1952670
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055555d7025c8 CR3: 000000002e28d000 CR4: 00000000003506f0
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
 rest_init+0x2e2/0x300 init/main.c:732
 arch_call_rest_init+0xe/0x10 init/main.c:829
 start_kernel+0x459/0x4e0 init/main.c:1074
 x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
 x86_64_start_kernel+0x60/0x60 arch/x86/kernel/head64.c:536
 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
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.