[PATCH net-next v2 6/6] selftests/vsock: test the netns assign privilege checks

[Bobby Eshleman <bobbyeshleman@gmail.com>]

From: Bobby Eshleman <bobbyeshleman@meta.com>

VSOCK_CMD_DEV_NETNS_SET 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>
---
Changes in v2:
- Assert only that the command fails, not EPERM: ynl's cli.py does not
  report the errno (Sashiko)
- Use ynl cli.py for the assign
---
 tools/testing/selftests/vsock/config    |  1 +
 tools/testing/selftests/vsock/vmtest.sh | 54 ++++++++++++++++++++++++++++++++-
 2 files changed, 54 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 e94cc2fd90cc..4f42bcdac3f6 100755
--- a/tools/testing/selftests/vsock/vmtest.sh
+++ b/tools/testing/selftests/vsock/vmtest.sh
@@ -81,6 +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
@@ -175,6 +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=(
@@ -187,6 +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")
 
@@ -335,7 +345,7 @@ check_args() {
 
 check_deps() {
 	for dep in vng ${QEMU} busybox pkill ssh ss socat nsenter unshare \
-		python3; do
+		setpriv python3; do
 		if [[ ! -x $(command -v "${dep}") ]]; then
 			echo -e "skip:    dependency ${dep} not found!\n"
 			exit "${KSFT_SKIP}"
@@ -1832,6 +1842,48 @@ 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" -- "${cmd}" python3 /root/ynl/cli.py --no-schema \
+		--spec /root/ynl/vsock.yaml --do dev-netns-set &>/dev/null
+	rc=$?
+
+	if [[ "${rc}" -eq 0 ]]; then
+		log_host "assign unexpectedly succeeded without CAP_NET_ADMIN"
+		return "${KSFT_FAIL}"
+	fi
+
+	return "${KSFT_PASS}"
+}
+
+test_ns_guest_assign_g2h_netns_unpriv_user_ns_fails() {
+	local unpriv_uid=65534
+	local unpriv
+	local rc
+
+	unpriv="setpriv --reuid=${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
+
+	vm_ssh "init_ns" -- "${unpriv} unshare -Urn" \
+		python3 /root/ynl/cli.py --no-schema \
+		--spec /root/ynl/vsock.yaml --do dev-netns-set &>/dev/null
+	rc=$?
+
+	if [[ "${rc}" -eq 0 ]]; then
+		log_host "assign unexpectedly succeeded for unprivileged user"
+		return "${KSFT_FAIL}"
+	fi
+
+	return "${KSFT_PASS}"
+}
+
 shared_vm_test() {
 	local tname
 

-- 
2.53.0-Meta