linux-kernel - Re: [syzbot] [kvmarm?] WARNING in kvm_set_vm_id

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Message-ID: <868qg6tldw.wl-maz@kernel.org>
Date: Sun, 16 Nov 2025 08:46:51 +0000
From: Marc Zyngier <maz@...nel.org>
To: syzbot <syzbot+c4aef6558d0cd90fe378@...kaller.appspotmail.com>
Cc: catalin.marinas@....com,
	joey.gouly@....com,
	kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	oliver.upton@...ux.dev,
	oupton@...nel.org,
	suzuki.poulose@....com,
	syzkaller-bugs@...glegroups.com,
	will@...nel.org,
	yuzenghui@...wei.com
Subject: Re: [syzbot] [kvmarm?] WARNING in kvm_set_vm_id_reg

On Sat, 15 Nov 2025 18:59:20 +0000,
syzbot <syzbot+c4aef6558d0cd90fe378@...kaller.appspotmail.com> wrote:
> 
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    7a0892d2836e Merge tag 'pci-v6.18-fixes-5' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12c56884580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bbf220ce32df0361
> dashboard link: https://syzkaller.appspot.com/bug?extid=c4aef6558d0cd90fe378
> compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=139c77cd980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11d6a914580000
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/fa3fbcfdac58/non_bootable_disk-7a0892d2.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/e83411b74df6/vmlinux-7a0892d2.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/135caed64c95/Image-7a0892d2.gz.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c4aef6558d0cd90fe378@...kaller.appspotmail.com
> 
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 3583 at arch/arm64/kvm/sys_regs.c:2353 kvm_set_vm_id_reg+0x60/0xf4 arch/arm64/kvm/sys_regs.c:2348
> Modules linked in:
> CPU: 1 UID: 0 PID: 3583 Comm: syz.2.17 Not tainted syzkaller #0 PREEMPT 
> Hardware name: linux,dummy-virt (DT)
> pstate: a1402009 (NzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> pc : kvm_set_vm_id_reg+0x60/0xf4 arch/arm64/kvm/sys_regs.c:2353
> lr : kvm_finalize_sys_regs+0x88/0x244 arch/arm64/kvm/sys_regs.c:5616
> sp : ffff800089543ab0
> x29: ffff800089543ab0 x28: f6f00000121c12c0 x27: 0000000000000000
> x26: 0000000000000000 x25: f1f00000085d8000 x24: 0000000000000000
> x23: f1f00000085d8048 x22: 0000000000000000 x21: f9ff800083e0dbd0
> x20: f9ff800083e0d000 x19: f1f00000085d8000 x18: 00000000ffffffff
> x17: 0000000000000000 x16: 0000000000000000 x15: ffff800089543a90
> x14: ffff800089543d98 x13: ffff800089543d5a x12: 0000000000000000
> x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000078
> x8 : ffff800089543da8 x7 : f0f0000004469ffc x6 : 0000000000000077
> x5 : f6f00000121c12c0 x4 : 0000000000000001 x3 : f9ff800083e0dd18
> x2 : 1101001020110222 x1 : 0000000000000000 x0 : f9ff800083e0d000
> Call trace:
>  kvm_set_vm_id_reg+0x60/0xf4 arch/arm64/kvm/sys_regs.c:2348 (P)
>  kvm_finalize_sys_regs+0x88/0x244 arch/arm64/kvm/sys_regs.c:5616
>  kvm_arch_vcpu_run_pid_change+0x8c/0x36c arch/arm64/kvm/arm.c:857
>  kvm_vcpu_ioctl+0x7f8/0x878 virt/kvm/kvm_main.c:4464
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:597 [inline]
>  __se_sys_ioctl fs/ioctl.c:583 [inline]
>  __arm64_sys_ioctl+0xac/0x104 fs/ioctl.c:583
>  __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
>  invoke_syscall+0x48/0x110 arch/arm64/kernel/syscall.c:49
>  el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:132
>  do_el0_svc+0x1c/0x28 arch/arm64/kernel/syscall.c:151
>  el0_svc+0x34/0x10c arch/arm64/kernel/entry-common.c:746
>  el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:765
>  el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:596
> ---[ end trace 0000000000000000 ]---

#syz fix KVM: arm64: Finalize ID registers only once per VM

	M.

-- 
Without deviation from the norm, progress is not possible.