From: Bobby Eshleman <bobbyeshleman@meta.com>

/dev/vsock IOCTL_VM_SOCKETS_ASSIGN_G2H_NETNS has refuses callers without
CAP_NET_ADMIN in the init user namespace.

Add two tests: one confirms that CAP_NET_ADMIN is required even by a
privileged user and the other confirms that CAP_NET_ADMIN in an
unprivileged user ns alone is insufficient.

CONFIG_USER_NS is needed to test the CAP_NET_ADMIN + unprivileged user
ns case.

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
---
 tools/testing/selftests/vsock/config    |  1 +
 tools/testing/selftests/vsock/vmtest.sh | 59 ++++++++++++++++++++++++++++++++-
 2 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vsock/config b/tools/testing/selftests/vsock/config
index 5f0a4f17dfc9..4b31085558fa 100644
--- a/tools/testing/selftests/vsock/config
+++ b/tools/testing/selftests/vsock/config
@@ -109,3 +109,4 @@ CONFIG_FS_DAX=y
 CONFIG_MEMORY_HOTPLUG=y
 CONFIG_MEMORY_HOTREMOVE=y
 CONFIG_ZONE_DEVICE=y
+CONFIG_USER_NS=y
diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh
index 53591fa07f1a..efb94d17d997 100755
--- a/tools/testing/selftests/vsock/vmtest.sh
+++ b/tools/testing/selftests/vsock/vmtest.sh
@@ -28,6 +28,7 @@ readonly WAIT_PERIOD=3
 readonly WAIT_PERIOD_MAX=60
 readonly WAIT_QEMU=5
 readonly PIDFILE_TEMPLATE=/tmp/vsock_vmtest_XXXX.pid
+readonly EPERM=1
 declare -A PIDFILES
 
 # virtme-ng offers a netdev for ssh when using "--ssh", but we also need a
@@ -80,6 +81,8 @@ readonly TEST_NAMES=(
 	ns_guest_assign_g2h_netns_host_connect_ok
 	ns_guest_assign_g2h_netns_reset_on_ns_delete_ok
 	ns_guest_assign_g2h_netns_old_conn_send_fails
+	ns_guest_assign_g2h_netns_no_cap_net_admin_fails
+	ns_guest_assign_g2h_netns_unpriv_user_ns_fails
 )
 readonly TEST_DESCS=(
 	# vm_server_host_client
@@ -174,6 +177,12 @@ readonly TEST_DESCS=(
 
 	# ns_guest_assign_g2h_netns_old_conn_send_fails
 	"Check connections made before the assign stop sending once they lose the device."
+
+	# ns_guest_assign_g2h_netns_no_cap_net_admin_fails
+	"Check assigning the guest's vsock device to a namespace needs CAP_NET_ADMIN."
+
+	# ns_guest_assign_g2h_netns_unpriv_user_ns_fails
+	"Check an unprivileged user cannot claim the guest's vsock device via a user ns."
 )
 
 readonly USE_SHARED_VM=(
@@ -186,6 +195,8 @@ readonly USE_SHARED_VM=(
 	ns_guest_assign_g2h_netns_host_connect_ok
 	ns_guest_assign_g2h_netns_reset_on_ns_delete_ok
 	ns_guest_assign_g2h_netns_old_conn_send_fails
+	ns_guest_assign_g2h_netns_no_cap_net_admin_fails
+	ns_guest_assign_g2h_netns_unpriv_user_ns_fails
 )
 readonly NS_MODES=("local" "global")
 
@@ -333,7 +344,8 @@ check_args() {
 }
 
 check_deps() {
-	for dep in vng ${QEMU} busybox pkill ssh ss socat nsenter unshare; do
+	for dep in vng ${QEMU} busybox pkill ssh ss socat nsenter unshare \
+		setpriv; do
 		if [[ ! -x $(command -v "${dep}") ]]; then
 			echo -e "skip:    dependency ${dep} not found!\n"
 			exit "${KSFT_SKIP}"
@@ -1805,6 +1817,51 @@ test_ns_guest_assign_g2h_netns_reset_on_ns_delete_ok() {
 	return "${KSFT_PASS}"
 }
 
+test_ns_guest_assign_g2h_netns_no_cap_net_admin_fails() {
+	local cmd="unshare -n setpriv --bounding-set=-net_admin"
+	local rc
+
+	vm_ssh "init_ns" -- "${cmd}" ./vsock_assign_g2h_netns &>/dev/null
+	rc=$?
+
+	if [[ "${rc}" -ne "${EPERM}" ]]; then
+		log_host "expected EPERM (${EPERM}) without CAP_NET_ADMIN, got ${rc}"
+		return "${KSFT_FAIL}"
+	fi
+
+	return "${KSFT_PASS}"
+}
+
+test_ns_guest_assign_g2h_netns_unpriv_user_ns_fails() {
+	local helper=/tmp/vsock_assign_g2h_netns
+	local unpriv_uid=65534
+	local unpriv
+	local rc
+
+	unpriv="setpriv --reuid=${unpriv_uid} --regid=${unpriv_uid}"
+	unpriv="${unpriv} --clear-groups"
+
+	if ! vm_ssh "init_ns" -- "${unpriv} unshare -U true"; then
+		log_host "unprivileged user namespaces unavailable, skipping"
+		return "${KSFT_SKIP}"
+	fi
+
+	# The home shared with the guest is root-only, so place the helper where
+	# an unprivileged user can execute it.
+	vm_ssh "init_ns" -- \
+		"cp ./vsock_assign_g2h_netns ${helper} && chmod 755 ${helper}"
+
+	vm_ssh "init_ns" -- "${unpriv} unshare -Urn ${helper}" &>/dev/null
+	rc=$?
+
+	if [[ "${rc}" -ne "${EPERM}" ]]; then
+		log_host "expected EPERM (${EPERM}) for an unprivileged user, got ${rc}"
+		return "${KSFT_FAIL}"
+	fi
+
+	return "${KSFT_PASS}"
+}
+
 shared_vm_test() {
 	local tname
 

-- 
2.53.0-Meta