Re: [syzbot] [virt?] WARNING in virtio_dev_remove

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jul 31, 2026 at 05:00:33PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    11028ab62899 Merge tag 'probes-fixes-v7.2-rc5' of git://gi..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=11c625b9580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cb17729fb04b1e3a
> dashboard link: https://syzkaller.appspot.com/bug?extid=a1c8effc62c569d4bd25
> 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=17405499580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1583649e580000

So I read this reproducer:


  memcpy((void*)0x200000000140, "sys/bus/pci/devices/0000:00:04.0/config\000",
         40);
  res = syscall(__NR_openat, /*fd=*/0xffffff9c, /*file=*/0x200000000140ul,
                /*flags=O_RDWR*/ 2, /*mode=*/0);
  if (res != -1)
    r[0] = res;
  //  pwrite64 arguments: [
  //    fd: fd (resource)
  //    buf: ptr[in, buffer] {
  //      buffer: {00 00} (length 0x2)
  //    }
  //    count: len = 0x2 (8 bytes)
  //    pos: intptr = 0x4 (8 bytes)
  //  ]
  memset((void*)0x200000000180, 0, 2);
  syscall(__NR_pwrite64, /*fd=*/r[0], /*buf=*/0x200000000180ul, /*count=*/2ul,
          /*pos=*/4ul);



So it writes 0 into pci command, effectively killing the device,
and then is unhappy that the driver prints warnings?
Who thought it's a good idea? Why?




> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/0afad3dd27f4/disk-11028ab6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/2e1441f9c31d/vmlinux-11028ab6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/5f0b8bdf00cd/bzImage-11028ab6.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+a1c8effc62c569d4bd25@syzkaller.appspotmail.com
> 
> ------------[ cut here ]------------
> dev->config->get_status(dev)
> WARNING: drivers/virtio/virtio.c:378 at virtio_dev_remove+0x18b/0x1b0 drivers/virtio/virtio.c:378, CPU#0: syz-executor501/5611
> Modules linked in:
> CPU: 0 UID: 0 PID: 5611 Comm: syz-executor501 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
> RIP: 0010:virtio_dev_remove+0x18b/0x1b0 drivers/virtio/virtio.c:378
> Code: 4c 89 f7 2e 2e 2e 41 ff d3 0c 01 0f b6 f0 4c 89 f7 4d 89 fb 5b 41 5c 41 5d 41 5e 41 5f 5d 2e e9 cb 7e c1 1a e8 96 50 87 fc 90 <0f> 0b 90 e9 6e ff ff ff 44 89 e9 80 e1 07 38 c1 0f 8c c2 fe ff ff
> RSP: 0018:ffffc9000430f7d8 EFLAGS: 00010293
> RAX: ffffffff853e8a5a RBX: ffff8880207766d0 RCX: ffff8880121c8000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 00000000000000ff R08: 0000000000000000 R09: 0000000000000000
> R10: dffffc0000000000 R11: ffffffff8540e710 R12: 1ffff110040eecda
> R13: dffffc0000000000 R14: ffff888020776000 R15: ffffffff8bd67c98
> FS:  0000555584740400(0000) GS:ffff888125c41000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fe020e42e9c CR3: 000000003c1e4000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  device_remove drivers/base/dd.c:616 [inline]
>  __device_release_driver drivers/base/dd.c:1349 [inline]
>  device_release_driver_internal+0x48b/0x880 drivers/base/dd.c:1372
>  bus_remove_device+0x449/0x560 drivers/base/bus.c:664
>  device_del+0x528/0x8f0 drivers/base/core.c:3961
>  device_unregister+0x21/0xf0 drivers/base/core.c:4002
>  unregister_virtio_device+0x37/0x60 drivers/virtio/virtio.c:594
>  virtio_pci_remove+0x7f/0xf0 drivers/virtio/virtio_pci_common.c:758
>  pci_device_remove+0x99/0x1c0 drivers/pci/pci-driver.c:512
>  device_remove drivers/base/dd.c:616 [inline]
>  __device_release_driver drivers/base/dd.c:1349 [inline]
>  device_release_driver_internal+0x48b/0x880 drivers/base/dd.c:1372
>  pci_stop_dev drivers/pci/remove.c:27 [inline]
>  pci_stop_bus_device+0xf6/0x120 drivers/pci/remove.c:93
>  pci_stop_and_remove_bus_device drivers/pci/remove.c:128 [inline]
>  pci_stop_and_remove_bus_device_locked+0x77/0xb0 drivers/pci/remove.c:136
>  remove_store+0xe5/0x150 drivers/pci/pci-sysfs.c:523
>  kernfs_fop_write_iter+0x3a5/0x540 fs/kernfs/file.c:345
>  new_sync_write fs/read_write.c:595 [inline]
>  vfs_write+0x61e/0xbb0 fs/read_write.c:687
>  ksys_write+0x156/0x270 fs/read_write.c:739
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f5f1782a589
> Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 d8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffded968938 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5f1782a589
> RDX: 0000000000000001 RSI: 0000200000000200 RDI: 0000000000000004
> RBP: 0000000000000001 R08: 0000000000000006 R09: 0000000000000006
> R10: 0000000000000006 R11: 0000000000000246 R12: 00007ffded968aa8
> R13: 431bde82d7b634db R14: 00007f5f178bdc40 R15: 0000000000000002
>  </TASK>
> 
> 
> ---
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