[v4] vhost-user: support any POSIX system (tested on macOS, FreeBSD, OpenBSD)

[PATCH v4 03/12] libvhost-user: mask F_INFLIGHT_SHMFD if memfd is not supported

Posted by Stefano Garzarella 6 months, 3 weeks ago

libvhost-user will panic when receiving VHOST_USER_GET_INFLIGHT_FD
message if MFD_ALLOW_SEALING is not defined, since it's not able
to create a memfd.

VHOST_USER_GET_INFLIGHT_FD is used only if
VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD is negotiated. So, let's mask
that feature if the backend is not able to properly handle these
messages.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 subprojects/libvhost-user/libvhost-user.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index a11afd1960..1c361ffd51 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -1674,6 +1674,16 @@ vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
         features |= dev->iface->get_protocol_features(dev);
     }
 
+    /*
+     * If MFD_ALLOW_SEALING is not defined, we are not able to handle
+     * VHOST_USER_GET_INFLIGHT_FD messages, since we can't create a memfd.
+     * Those messages are used only if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD
+     * is negotiated. A device implementation can enable it, so let's mask
+     * it to avoid a runtime panic.
+     */
+#ifndef MFD_ALLOW_SEALING
+    features &= ~(1ULL << VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD);
+#endif
     vmsg_set_reply_u64(vmsg, features);
     return true;
 }
-- 
2.45.0

Re: [PATCH v4 03/12] libvhost-user: mask F_INFLIGHT_SHMFD if memfd is not supported

Posted by Philippe Mathieu-Daudé 6 months, 3 weeks ago

On 8/5/24 09:44, Stefano Garzarella wrote:
> libvhost-user will panic when receiving VHOST_USER_GET_INFLIGHT_FD
> message if MFD_ALLOW_SEALING is not defined, since it's not able
> to create a memfd.
> 
> VHOST_USER_GET_INFLIGHT_FD is used only if
> VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD is negotiated. So, let's mask
> that feature if the backend is not able to properly handle these
> messages.
> 
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>   subprojects/libvhost-user/libvhost-user.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index a11afd1960..1c361ffd51 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -1674,6 +1674,16 @@ vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
>           features |= dev->iface->get_protocol_features(dev);
>       }
>   

Maybe move the #ifndef here?

> +    /*
> +     * If MFD_ALLOW_SEALING is not defined, we are not able to handle
> +     * VHOST_USER_GET_INFLIGHT_FD messages, since we can't create a memfd.
> +     * Those messages are used only if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD
> +     * is negotiated. A device implementation can enable it, so let's mask
> +     * it to avoid a runtime panic.
> +     */
> +#ifndef MFD_ALLOW_SEALING
> +    features &= ~(1ULL << VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD);
> +#endif
>       vmsg_set_reply_u64(vmsg, features);
>       return true;
>   }

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Re: [PATCH v4 03/12] libvhost-user: mask F_INFLIGHT_SHMFD if memfd is not supported

Posted by Stefano Garzarella 6 months, 2 weeks ago

On Wed, May 08, 2024 at 12:39:33PM GMT, Philippe Mathieu-Daudé wrote:
>On 8/5/24 09:44, Stefano Garzarella wrote:
>>libvhost-user will panic when receiving VHOST_USER_GET_INFLIGHT_FD
>>message if MFD_ALLOW_SEALING is not defined, since it's not able
>>to create a memfd.
>>
>>VHOST_USER_GET_INFLIGHT_FD is used only if
>>VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD is negotiated. So, let's mask
>>that feature if the backend is not able to properly handle these
>>messages.
>>
>>Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>>---
>>  subprojects/libvhost-user/libvhost-user.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>>diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
>>index a11afd1960..1c361ffd51 100644
>>--- a/subprojects/libvhost-user/libvhost-user.c
>>+++ b/subprojects/libvhost-user/libvhost-user.c
>>@@ -1674,6 +1674,16 @@ vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
>>          features |= dev->iface->get_protocol_features(dev);
>>      }
>
>Maybe move the #ifndef here?

Yep, I'll do.

>
>>+    /*
>>+     * If MFD_ALLOW_SEALING is not defined, we are not able to handle
>>+     * VHOST_USER_GET_INFLIGHT_FD messages, since we can't create a memfd.
>>+     * Those messages are used only if VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD
>>+     * is negotiated. A device implementation can enable it, so let's mask
>>+     * it to avoid a runtime panic.
>>+     */
>>+#ifndef MFD_ALLOW_SEALING
>>+    features &= ~(1ULL << VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD);
>>+#endif
>>      vmsg_set_reply_u64(vmsg, features);
>>      return true;
>>  }
>
>Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>

Thanks,
Stefano