Re: [PATCH] virtio-mmio: fix guest kernel crash with SHM regions

2021-01-23 Thread Laurent Vivier 
Anyone to merge this?

Thanks,
Laurent

Le 20/12/2020 à 17:35, Laurent Vivier a écrit :
> In the kernel, virtio_gpu_init() uses virtio_get_shm_region()
> since
> commit 6076a9711dc5 ("drm/virtio: implement blob resources: probe for host 
> visible region")
> but vm_get_shm_region() unconditionally uses VIRTIO_MMIO_SHM_SEL to
> get the address and the length of the region.
> 
> commit 38e895487afc ("virtio: Implement get_shm_region for MMIO transport"
> 
> As this is not implemented in QEMU, address and length are 0 and passed
> as is to devm_request_mem_region() that triggers a crash:
> 
>   [drm:virtio_gpu_init] *ERROR* Could not reserve host visible region
>   Unable to handle kernel NULL pointer dereference at virtual address (ptrval)
> 
> According to the comments in the kernel, a non existent shared region
> has a length of (u64)-1.
> 
> This is what we return now with this patch to disable the region.
> 
> Signed-off-by: Laurent Vivier 
> ---
>  hw/virtio/virtio-mmio.c | 8 
>  1 file changed, 8 insertions(+)
> 
> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
> index e1b5c3b81e37..610661d6a526 100644
> --- a/hw/virtio/virtio-mmio.c
> +++ b/hw/virtio/virtio-mmio.c
> @@ -191,6 +191,14 @@ static uint64_t virtio_mmio_read(void *opaque, hwaddr 
> offset, unsigned size)
>  return 0;
>  }
>  return vdev->generation;
> +   case VIRTIO_MMIO_SHM_LEN_LOW:
> +   case VIRTIO_MMIO_SHM_LEN_HIGH:
> +/*
> + * VIRTIO_MMIO_SHM_SEL is unimplemented
> + * according to the linux driver, if region length is -1
> + * the shared memory doesn't exist
> + */
> +return -1;
>  case VIRTIO_MMIO_DEVICE_FEATURES_SEL:
>  case VIRTIO_MMIO_DRIVER_FEATURES:
>  case VIRTIO_MMIO_DRIVER_FEATURES_SEL:
>

Re: [PATCH] virtio-mmio: fix guest kernel crash with SHM regions

2021-01-08 Thread Stefano Garzarella 

On Sun, Dec 20, 2020 at 05:35:39PM +0100, Laurent Vivier wrote:

In the kernel, virtio_gpu_init() uses virtio_get_shm_region()
since
commit 6076a9711dc5 ("drm/virtio: implement blob resources: probe for host visible 
region")
but vm_get_shm_region() unconditionally uses VIRTIO_MMIO_SHM_SEL to
get the address and the length of the region.

commit 38e895487afc ("virtio: Implement get_shm_region for MMIO transport"

As this is not implemented in QEMU, address and length are 0 and passed
as is to devm_request_mem_region() that triggers a crash:

 [drm:virtio_gpu_init] *ERROR* Could not reserve host visible region
 Unable to handle kernel NULL pointer dereference at virtual address (ptrval)

According to the comments in the kernel, a non existent shared region
has a length of (u64)-1.

This is what we return now with this patch to disable the region.

Signed-off-by: Laurent Vivier 
---
hw/virtio/virtio-mmio.c | 8 
1 file changed, 8 insertions(+)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index e1b5c3b81e37..610661d6a526 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -191,6 +191,14 @@ static uint64_t virtio_mmio_read(void *opaque, hwaddr 
offset, unsigned size)
return 0;
}
return vdev->generation;
+   case VIRTIO_MMIO_SHM_LEN_LOW:
+   case VIRTIO_MMIO_SHM_LEN_HIGH:
+/*
+ * VIRTIO_MMIO_SHM_SEL is unimplemented
+ * according to the linux driver, if region length is -1
+ * the shared memory doesn't exist
+ */
+return -1;
case VIRTIO_MMIO_DEVICE_FEATURES_SEL:
case VIRTIO_MMIO_DRIVER_FEATURES:
case VIRTIO_MMIO_DRIVER_FEATURES_SEL:
--
2.29.2




Reviewed-by: Stefano Garzarella

Re: [PATCH] virtio-mmio: fix guest kernel crash with SHM regions

2021-01-07 Thread Gerd Hoffmann 
  Hi,

> > According to the comments in the kernel, a non existent shared region
> > has a length of (u64)-1.

virtio spec says the same.

> > +   case VIRTIO_MMIO_SHM_LEN_LOW:
> > +   case VIRTIO_MMIO_SHM_LEN_HIGH:
> > +/*
> > + * VIRTIO_MMIO_SHM_SEL is unimplemented
> > + * according to the linux driver, if region length is -1
> > + * the shared memory doesn't exist
> > + */
> > +return -1;

Acked-by: Gerd Hoffmann 

take care,
  Gerd

Re: [PATCH] virtio-mmio: fix guest kernel crash with SHM regions

2021-01-07 Thread Laurent Vivier 
Hi,

any comment?

Thanks,
Laurent

Le 20/12/2020 à 17:35, Laurent Vivier a écrit :
> In the kernel, virtio_gpu_init() uses virtio_get_shm_region()
> since
> commit 6076a9711dc5 ("drm/virtio: implement blob resources: probe for host 
> visible region")
> but vm_get_shm_region() unconditionally uses VIRTIO_MMIO_SHM_SEL to
> get the address and the length of the region.
> 
> commit 38e895487afc ("virtio: Implement get_shm_region for MMIO transport"
> 
> As this is not implemented in QEMU, address and length are 0 and passed
> as is to devm_request_mem_region() that triggers a crash:
> 
>   [drm:virtio_gpu_init] *ERROR* Could not reserve host visible region
>   Unable to handle kernel NULL pointer dereference at virtual address (ptrval)
> 
> According to the comments in the kernel, a non existent shared region
> has a length of (u64)-1.
> 
> This is what we return now with this patch to disable the region.
> 
> Signed-off-by: Laurent Vivier 
> ---
>  hw/virtio/virtio-mmio.c | 8 
>  1 file changed, 8 insertions(+)
> 
> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
> index e1b5c3b81e37..610661d6a526 100644
> --- a/hw/virtio/virtio-mmio.c
> +++ b/hw/virtio/virtio-mmio.c
> @@ -191,6 +191,14 @@ static uint64_t virtio_mmio_read(void *opaque, hwaddr 
> offset, unsigned size)
>  return 0;
>  }
>  return vdev->generation;
> +   case VIRTIO_MMIO_SHM_LEN_LOW:
> +   case VIRTIO_MMIO_SHM_LEN_HIGH:
> +/*
> + * VIRTIO_MMIO_SHM_SEL is unimplemented
> + * according to the linux driver, if region length is -1
> + * the shared memory doesn't exist
> + */
> +return -1;
>  case VIRTIO_MMIO_DEVICE_FEATURES_SEL:
>  case VIRTIO_MMIO_DRIVER_FEATURES:
>  case VIRTIO_MMIO_DRIVER_FEATURES_SEL:
>

[PATCH] virtio-mmio: fix guest kernel crash with SHM regions

2020-12-20 Thread Laurent Vivier 
In the kernel, virtio_gpu_init() uses virtio_get_shm_region()
since
commit 6076a9711dc5 ("drm/virtio: implement blob resources: probe for host 
visible region")
but vm_get_shm_region() unconditionally uses VIRTIO_MMIO_SHM_SEL to
get the address and the length of the region.

commit 38e895487afc ("virtio: Implement get_shm_region for MMIO transport"

As this is not implemented in QEMU, address and length are 0 and passed
as is to devm_request_mem_region() that triggers a crash:

  [drm:virtio_gpu_init] *ERROR* Could not reserve host visible region
  Unable to handle kernel NULL pointer dereference at virtual address (ptrval)

According to the comments in the kernel, a non existent shared region
has a length of (u64)-1.

This is what we return now with this patch to disable the region.

Signed-off-by: Laurent Vivier 
---
 hw/virtio/virtio-mmio.c | 8 
 1 file changed, 8 insertions(+)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index e1b5c3b81e37..610661d6a526 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -191,6 +191,14 @@ static uint64_t virtio_mmio_read(void *opaque, hwaddr 
offset, unsigned size)
 return 0;
 }
 return vdev->generation;
+   case VIRTIO_MMIO_SHM_LEN_LOW:
+   case VIRTIO_MMIO_SHM_LEN_HIGH:
+/*
+ * VIRTIO_MMIO_SHM_SEL is unimplemented
+ * according to the linux driver, if region length is -1
+ * the shared memory doesn't exist
+ */
+return -1;
 case VIRTIO_MMIO_DEVICE_FEATURES_SEL:
 case VIRTIO_MMIO_DRIVER_FEATURES:
 case VIRTIO_MMIO_DRIVER_FEATURES_SEL:
-- 
2.29.2