[PATCH v2 0/2] virtio-pci: add check for vdev in virtio_pci_isr_read

[PATCH v2 0/2] virtio-pci: add check for vdev in virtio_pci_isr_read

[Yuri Benditovich]

This commit completes the solution of segfault in hot unplug flow
(by commit ccec7e9603f446fe75c6c563ba335c00cfda6a06).
Added missing check for vdev in virtio_pci_isr_read.

v1->v2:
Added crash stack
Updated commit comment
Cosmetic change in additional procedure in this file per request
of Philippe Mathieu-Daude

Yuri Benditovich (2):
  virtio-pci: add check for vdev in virtio_pci_isr_read
  virtio-pci: remove explicit initialization of val

 hw/virtio/virtio-pci.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

-- 
2.17.1

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

[Yuri Benditovich]

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

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

[Yuri Benditovich]

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
>

[PATCH v2 2/2] virtio-pci: remove explicit initialization of val

[Yuri Benditovich]

The value is assigned later in this procedure.

Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
---
 hw/virtio/virtio-pci.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index 4a3dcee771..c1b67cf6fc 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1385,10 +1385,10 @@ static uint64_t virtio_pci_device_read(void *opaque, hwaddr addr,
 {
     VirtIOPCIProxy *proxy = opaque;
     VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
-    uint64_t val = 0;
+    uint64_t val;
 
     if (vdev == NULL) {
-        return val;
+        return 0;
     }
 
     switch (size) {
@@ -1401,6 +1401,9 @@ static uint64_t virtio_pci_device_read(void *opaque, hwaddr addr,
     case 4:
         val = virtio_config_modern_readl(vdev, addr);
         break;
+    default:
+        val = 0;
+        break;
     }
     return val;
 }
-- 
2.17.1