[v6.6] INFO: rcu detected stall in sys_munmap (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3b9f64db0496 Linux 6.6.138
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10c823ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5b35c4db8465904
dashboard link: https://syzkaller.appspot.com/bug?extid=4805acafe4af1e1be281
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9e5afbe648d5/disk-3b9f64db.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c3607dd9b93c/vmlinux-3b9f64db.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f0392d8b3ded/bzImage-3b9f64db.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4805ac...@syzkaller.appspotmail.com

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>


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