[PATCH 17/25] virtiofsd: move to an empty network namespace

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: Stefan Hajnoczi <stefanha@redhat.com>

If the process is compromised there should be no network access.  Use an
empty network namespace to sandbox networking.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 contrib/virtiofsd/passthrough_ll.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthrough_ll.c
index 20a34d4d83..58cf82a89f 100644
--- a/contrib/virtiofsd/passthrough_ll.c
+++ b/contrib/virtiofsd/passthrough_ll.c
@@ -1822,6 +1822,19 @@ static void print_capabilities(void)
 	printf("}\n");
 }
 
+/*
+ * Called after our UNIX domain sockets have been created, now we can move to
+ * an empty network namespace to prevent TCP/IP and other network activity in
+ * case this process is compromised.
+ */
+static void setup_net_namespace(void)
+{
+	if (unshare(CLONE_NEWNET) != 0) {
+		fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWNET): %m\n");
+		exit(1);
+	}
+}
+
 /* This magic is based on lxc's lxc_pivot_root() */
 static void setup_pivot_root(const char *source)
 {
@@ -1913,6 +1926,7 @@ static void setup_mount_namespace(const char *source)
  */
 static void setup_sandbox(struct lo_data *lo)
 {
+	setup_net_namespace();
 	setup_mount_namespace(lo->source);
 }
 
-- 
2.23.0