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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0bbbd97a442d Linux 6.6.112
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10051734580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=463b5f1343c74e3819d3
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7e387d57d751/disk-0bbbd97a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/810d42505365/vmlinux-0bbbd97a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5d2fe115c227/bzImage-0bbbd97a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+463b5f...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6391/1:b..l
rcu: (detected by 0, t=10502 jiffies, g=15809, q=493 ncpus=2)
task:rm state:R running task stack:24968 pid:6391 ppid:6345 flags:0x00004000
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:lock_is_held_type+0x13e/0x190 kernel/locking/lockdep.c:5830
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc90004bdf4d8 EFLAGS: 00000206
RAX: 6835f053928c4c00 RBX: ffff88802340da00 RCX: 6835f053928c4c00
RDX: 0000000000000000 RSI: ffffffff8aaace60 RDI: ffffffff8afc64c0
RBP: 0000000000000000 R08: dffffc0000000000 R09: 1ffffffff21b4ea0
R10: dffffc0000000000 R11: fffffbfff21b4ea1 R12: 0000000000000002
R13: 0000000000000246 R14: ffffffff8cd59888 R15: ffff88802340e530
lock_is_held include/linux/lockdep.h:288 [inline]
task_css include/linux/cgroup.h:436 [inline]
mem_cgroup_from_task+0x62/0x110 mm/memcontrol.c:1009
get_obj_cgroup_from_current+0x167/0x280 mm/memcontrol.c:3033
memcg_slab_pre_alloc_hook mm/slab.h:492 [inline]
slab_pre_alloc_hook+0x95/0x310 mm/slab.h:719
slab_alloc_node mm/slub.c:3477 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc+0x5a/0x2e0 mm/slub.c:3519
vma_lock_alloc kernel/fork.c:460 [inline]
vm_area_dup+0x61/0x270 kernel/fork.c:513
__split_vma+0x19f/0xc00 mm/mmap.c:2373
do_vmi_align_munmap+0x2dc/0x1660 mm/mmap.c:2501
do_vmi_munmap+0x252/0x2d0 mm/mmap.c:2660
__mmap_region mm/mmap.c:2710 [inline]
mmap_region+0x741/0x2020 mm/mmap.c:2941
do_mmap+0x92f/0x10a0 mm/mmap.c:1385
vm_mmap_pgoff+0x1c0/0x400 mm/util.c:556
ksys_mmap_pgoff+0x520/0x700 mm/mmap.c:1431
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: 0033:0x7fbc81b09242
RSP: 002b:00007ffdec9b1708 EFLAGS: 00000206 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007fbc81a33000 RCX: 00007fbc81b09242
RDX: 0000000000000005 RSI: 0000000000086000 RDI: 00007fbc81a33000
RBP: 0000000000000812 R08: 0000000000000003 R09: 0000000000010000
R10: 0000000000000812 R11: 0000000000000206 R12: 00007ffdec9b1758
R13: 00007fbc81ae50c0 R14: 00007ffdec9b1b10 R15: 00000fffbd9362e4
</TASK>
rcu: rcu_preempt kthread starved for 10114 jiffies! g15809 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: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:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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 43 b9 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:ffffffff8ca07d80 EFLAGS: 000002c2
RAX: 24111870d41a4d00 RBX: ffffffff8161858b RCX: 24111870d41a4d00
RDX: 0000000000000001 RSI: ffffffff8aaabce0 RDI: ffffffff8afc64c0
RBP: ffffffff8ca07eb8 R08: ffff8880b8e36b2b R09: 1ffff110171c6d65
R10: dffffc0000000000 R11: ffffed10171c6d66 R12: ffffffff8e4a8568
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffffffff1952670
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000001f030 CR3: 000000002e4f6000 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>


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