Re: [PATCH v2 1/2] virtio-pci: add check for vdev in virtio_pci_isr_read

[Yuri Benditovich <yuri.benditovich@daynix.com>]

Ping


On Mon, Mar 15, 2021 at 1:59 PM Yuri Benditovich
<yuri.benditovich@daynix.com> wrote:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1743098
> This commit completes the solution of segfault in hot unplug flow
> (by commit ccec7e9603f446fe75c6c563ba335c00cfda6a06).
> Added missing check for vdev in virtio_pci_isr_read.
> Typical stack of crash:
> virtio_pci_isr_read ../hw/virtio/virtio-pci.c:1365 with proxy-vdev = 0
> memory_region_read_accessor at ../softmmu/memory.c:442
> access_with_adjusted_size at ../softmmu/memory.c:552
> memory_region_dispatch_read1 at ../softmmu/memory.c:1420
> memory_region_dispatch_read  at ../softmmu/memory.c:1449
> flatview_read_continue at ../softmmu/physmem.c:2822
> flatview_read at ../softmmu/physmem.c:2862
> address_space_read_full at ../softmmu/physmem.c:2875
>
> Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
> ---
>  hw/virtio/virtio-pci.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index 883045a223..4a3dcee771 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -1364,9 +1364,14 @@ static uint64_t virtio_pci_isr_read(void *opaque, hwaddr addr,
>  {
>      VirtIOPCIProxy *proxy = opaque;
>      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> -    uint64_t val = qatomic_xchg(&vdev->isr, 0);
> -    pci_irq_deassert(&proxy->pci_dev);
> +    uint64_t val;
> +
> +    if (vdev == NULL) {
> +        return 0;
> +    }
>
> +    val = qatomic_xchg(&vdev->isr, 0);
> +    pci_irq_deassert(&proxy->pci_dev);
>      return val;
>  }
>
> --
> 2.17.1
>