vhost-user: support any POSIX system (tested on macOS and FreeBSD)

[PATCH 3/9] libvhost-user: mask F_INFLIGHT_SHMFD if memfd is not supported

Stefano Garzarella posted 9 patches 9 months ago

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Maintainers: David Hildenbrand <david@redhat.com>, Igor Mammedov <imammedo@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Raphael Norwitz <raphael@enfabrica.net>, Paolo Bonzini <pbonzini@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Hanna Reitz <hreitz@redhat.com>, Jason Wang <jasowang@redhat.com>, "Marc-André Lureau" <marcandre.lureau@redhat.com>, "Daniel P. Berrangé" <berrange@redhat.com>, Thomas Huth <thuth@redhat.com>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Eric Blake <eblake@redhat.com>, Markus Armbruster <armbru@redhat.com>, Eduardo Habkost <eduardo@habkost.net>, Coiby Xu <Coiby.Xu@gmail.com>

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[PATCH 3/9] libvhost-user: mask F_INFLIGHT_SHMFD if memfd is not supported

Posted by Stefano Garzarella 9 months 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 527a550345..5da8de838b 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -1610,6 +1610,16 @@ 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;
 }
-- 
2.43.2