[PULL,v3,49/85] libvhost-user: mask F_INFLIGHT_SHMFD if memfd is not supported

Commit Message

Michael S. Tsirkin July 3, 2024, 10:48 p.m. UTC

From: Stefano Garzarella <[e-mail]>

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.

Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Tested-by: Philippe Mathieu-Daudé <[e-mail]>
Acked-by: Stefan Hajnoczi <[e-mail]>
Reviewed-by: David Hildenbrand <[e-mail]>
Signed-off-by: Stefano Garzarella <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Michael S. Tsirkin <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>
---
 subprojects/libvhost-user/libvhost-user.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Patch

diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index ea27683dac..9c630c2170 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -1674,6 +1674,17 @@  vu_get_protocol_features_exec(VuDev *dev, VhostUserMsg *vmsg)
         features |= dev->iface->get_protocol_features(dev);
     }
 
+#ifndef MFD_ALLOW_SEALING
+    /*
+     * 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.
+     */
+    features &= ~(1ULL << VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD);
+#endif
+
     vmsg_set_reply_u64(vmsg, features);
     return true;
 }