[igt-dev] [PATCH i-g-t] tests/core_unauth_vs_render: new test for the relaxed DRM_AUTH handling

[Emil Velikov]

From: Emil Velikov <emil.velikov at collabora.com>

As the inline comment says, this test checks that the kernel allows
unauthenticated master with render capable, RENDER_ALLOW ioctls.

The kernel commit has extra details why.

v2:

- drop RUN_AS_ROOT guard
- call check_auth() on the {,un}authenticated device
- check the device is PRIME (import) capable
- check the device has render node
- tweak expectations based on above three
- elaborate why we care only about -EACCES

Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
---
 tests/core_unauth_vs_render.c | 182 ++++++++++++++++++++++++++++++++++
 tests/meson.build             |   1 +
 2 files changed, 183 insertions(+)
 create mode 100644 tests/core_unauth_vs_render.c

diff --git a/tests/core_unauth_vs_render.c b/tests/core_unauth_vs_render.c
new file mode 100644
index 00000000..82dd2ce9
--- /dev/null
+++ b/tests/core_unauth_vs_render.c
@@ -0,0 +1,182 @@
+/*
+ * Copyright 2018 Collabora, Ltd
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *   Emil Velikov <emil.velikov at collabora.com>
+ */
+
+/*
+ * Testcase: Render capable, unauthenticated master doesn't throw -EACCES for
+ * DRM_RENDER_ALLOW ioctls.
+ */
+
+#include "igt.h"
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+#include <sys/poll.h>
+#include <sys/resource.h>
+#include <sys/sysmacros.h>
+#include "drm.h"
+
+#ifdef __linux__
+# include <sys/syscall.h>
+#else
+# include <pthread.h>
+#endif
+
+/* Checks whether the thread id is the current thread */
+static bool
+is_local_tid(pid_t tid)
+{
+#ifndef __linux__
+	return pthread_self() == tid;
+#else
+	/* On Linux systems, drmGetClient() would return the thread ID instead
+	   of the actual process ID */
+	return syscall(SYS_gettid) == tid;
+#endif
+}
+
+
+static bool check_auth(int fd)
+{
+	pid_t client_pid;
+	int i, auth, pid, uid;
+	unsigned long magic, iocs;
+	bool is_authenticated = false;
+
+	client_pid = getpid();
+	for (i = 0; !is_authenticated; i++) {
+		if (drmGetClient(fd, i, &auth, &pid, &uid, &magic, &iocs) != 0)
+			break;
+		is_authenticated = auth && (pid == client_pid || is_local_tid(pid));
+	}
+	return is_authenticated;
+}
+
+
+static bool has_prime_import(int fd)
+{
+	uint64_t value;
+
+	if (drmGetCap(fd, DRM_CAP_PRIME, &value))
+		return false;
+
+	return value & DRM_PRIME_CAP_IMPORT;
+}
+
+static bool has_render_node(int fd)
+{
+	char node_name[80];
+	struct stat sbuf;
+
+	if (fstat(fd, &sbuf))
+		return false;
+
+	sprintf(node_name, "/dev/dri/renderD%d", minor(sbuf.st_rdev) | 0x80);
+	if (stat(node_name, &sbuf))
+		return false;
+
+	return true;
+}
+
+IGT_TEST_DESCRIPTION("Call drmPrimeFDToHandle() from unauthenticated master doesn't return -EACCES.");
+
+static void test_unauth_vs_render(int master)
+{
+	int slave;
+	int prime_fd = -1;
+	uint32_t handle;
+
+	/*
+	 * The second open() happens without CAP_SYS_ADMIN, thus it will NOT
+	 * be authenticated.
+	 */
+	igt_info("Openning card node from a non-priv. user.\n");
+	igt_info("On failure, double-check the node permissions\n");
+	/* FIXME: relate to the master given and fix all of IGT */
+	slave = drm_open_driver(DRIVER_ANY);
+
+	igt_require(slave >= 0);
+	igt_assert(check_auth(slave) == false);
+
+	/* Issuing the following ioctl will fail, no doubt about it. */
+	igt_assert(drmPrimeFDToHandle(slave, prime_fd, &handle) < 0);
+
+	/*
+	 * Updated kernels allow render capable, unauthenticated master to
+	 * issue DRM_AUTH ioctls (like the above), as long as they are
+	 * annotated as DRM_RENDER_ALLOW - just like FD2HANDLE above.
+	 *
+	 * Otherwise, errno is set to -EACCES
+	 *
+	 * Note: We are _not_ interested in the FD2HANDLE specific errno. Those
+	 * should be checked other standalone tests.
+	 */
+	bool imp = has_prime_import(slave);
+	bool rend = has_render_node(slave);
+	igt_info("import %d rend %d\n", imp, rend);
+	if (has_prime_import(slave) && has_render_node(slave))
+		igt_assert(errno != EACCES);
+
+	else
+		igt_assert(errno == EACCES);
+
+	close(slave);
+}
+
+/*
+ * IGT is executed as root, although that may(?) change in the future.
+ * Thus we need to drop the privileges so that the second open() results in a
+ * client which is not unauthenticated. Running as normal user circumvents that.
+ *
+ * In both cases, we need to ensure the file permissions of the node are
+ * sufficient.
+ */
+
+igt_main
+{
+	int master;
+
+	igt_fixture
+		master = drm_open_driver(DRIVER_ANY);
+
+	igt_assert(check_auth(master) == true);
+
+	igt_subtest("unauth-vs-render") {
+		igt_fork(child, 1) {
+			igt_drop_root();
+			test_unauth_vs_render(master);
+		}
+		igt_waitchildren();
+	}
+}
diff --git a/tests/meson.build b/tests/meson.build
index 0f12df26..e5200b36 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -1,5 +1,6 @@
 test_progs = [
 	'core_auth',
+	'core_unauth_vs_render',
 	'core_getclient',
 	'core_getstats',
 	'core_getversion',
-- 
2.20.1