Re: [syzbot] [kvm?] BUG: sleeping function called from invalid context in kvm_mmu_notifier_invalidate_range_start

[Lorenzo Stoakes (ARM)]

 +cc Sebastian

On Wed, Sep 16, 2026 at 07:08:26AM -0700, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    9b87fdc9af2f Merge tag 'sched_ext-for-7.3-rc3-fixes' of gi..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16f46bf9580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b454dc6b1b7acd30
> dashboard link: https://syzkaller.appspot.com/bug?extid=c3178b6b512446632bac
> compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12f23925580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16f23925580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d9d20c79bd3c/disk-9b87fdc9.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/2a6a8f176798/vmlinux-9b87fdc9.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/db8864d1c812/bzImage-9b87fdc9.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c3178b6b512446632bac@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
> in_atomic(): 0, irqs_disabled(): 0, non_block: 1, pid: 38, name: oom_reaper
> preempt_count: 0, expected: 0
> RCU nest depth: 0, expected: 0
> locks held by oom_reaper/38: 4, last CPU#1:
>  #0: ffff8880370147b0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:619 [inline]
>  #0: ffff8880370147b0 (&mm->mmap_lock){++++}-{4:4}, at: oom_reap_task_mm mm/oom_kill.c:566 [inline]
>  #0: ffff8880370147b0 (&mm->mmap_lock){++++}-{4:4}, at: oom_reap_task mm/oom_kill.c:609 [inline]
>  #0: ffff8880370147b0 (&mm->mmap_lock){++++}-{4:4}, at: oom_reaper+0x2b4/0xc10 mm/oom_kill.c:650
>  #1: ffffffff8e30af80 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: mmu_notifier_invalidate_range_start_nonblock include/linux/mmu_notifier.h:495 [inline]
>  #1: ffffffff8e30af80 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}, at: zap_vma_for_reaping+0x193/0x380 mm/memory.c:2266
>  #2: ffffffff8e30afd8 (srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:198 [inline]
>  #2: ffffffff8e30afd8 (srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:305 [inline]
>  #2: ffffffff8e30afd8 (srcu){.+.+}-{0:0}, at: mn_hlist_invalidate_range_start mm/mmu_notifier.c:515 [inline]
>  #2: ffffffff8e30afd8 (srcu){.+.+}-{0:0}, at: __mmu_notifier_invalidate_range_start+0x5c6/0xb80 mm/mmu_notifier.c:580
>  #3: ffff8880465ad560 (&kvm->mn_invalidate_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:45 [inline]
>  #3: ffff8880465ad560 (&kvm->mn_invalidate_lock){+.+.}-{3:3}, at: kvm_mmu_notifier_invalidate_range_start+0x1b6/0xc10 virt/kvm/kvm_main.c:745
> CPU: 1 UID: 0 PID: 38 Comm: oom_reaper Not tainted syzkaller #0 PREEMPT_{RT,(full)}
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
>  __might_resched+0x31b/0x470 kernel/sched/core.c:9257
>  __rt_spin_lock kernel/locking/spinlock_rt.c:48 [inline]

Seems like a false positive and an RT thing?

Seems like [0] addresses it?

[0]:https://lore.kernel.org/all/20260916155105.qDi2MiYW@xxxxxxxxxxxxx/

>  rt_spin_lock+0xc2/0x400 kernel/locking/spinlock_rt.c:57
>  spin_lock include/linux/spinlock_rt.h:45 [inline]
>  kvm_mmu_notifier_invalidate_range_start+0x1b6/0xc10 virt/kvm/kvm_main.c:745
>  mn_hlist_invalidate_range_start mm/mmu_notifier.c:525 [inline]
>  __mmu_notifier_invalidate_range_start+0x709/0xb80 mm/mmu_notifier.c:580
>  mmu_notifier_invalidate_range_start_nonblock include/linux/mmu_notifier.h:498 [inline]
>  zap_vma_for_reaping+0x1f7/0x380 mm/memory.c:2266
>  __oom_reap_task_mm mm/oom_kill.c:548 [inline]
>  oom_reap_task_mm mm/oom_kill.c:585 [inline]
>  oom_reap_task mm/oom_kill.c:609 [inline]
>  oom_reaper+0x519/0xc10 mm/oom_kill.c:650
>  kthread+0x38b/0x470 kernel/kthread.c:436
>  ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>  </TASK>
> oom_reaper: reaped process 8617 (syz.2.1028), now anon-rss:0kB, file-rss:72kB, shmem-rss:0kB
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

OK I attach the patch, so:

#syz test

--
Cheers, Lorenzo