selftests/ovl: add second selftest for "override_creds"

Add a simple test to verify that the new "override_creds" option works.

Link: https://lore.kernel.org/r/20250219-work-overlayfs-v3-3-46af55e4ceda@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c

@@ -6,27 +6,35 @@
 #include <sched.h>
 #include <stdio.h>
 #include <string.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/mount.h>
 #include <unistd.h>
 
 #include "../../kselftest_harness.h"
 #include "../../pidfd/pidfd.h"
 #include "log.h"
+#include "../utils.h"
 #include "wrappers.h"
 
 FIXTURE(set_layers_via_fds) {
+	int pidfd;
 };
 
 FIXTURE_SETUP(set_layers_via_fds)
 {
-	ASSERT_EQ(mkdir("/set_layers_via_fds", 0755), 0);
+	self->pidfd = -EBADF;
+	EXPECT_EQ(mkdir("/set_layers_via_fds", 0755), 0);
 }
 
 FIXTURE_TEARDOWN(set_layers_via_fds)
 {
+	if (self->pidfd >= 0) {
+		EXPECT_EQ(sys_pidfd_send_signal(self->pidfd, SIGKILL, NULL, 0), 0);
+		EXPECT_EQ(close(self->pidfd), 0);
+	}
 	umount2("/set_layers_via_fds", 0);
-	ASSERT_EQ(rmdir("/set_layers_via_fds"), 0);
+	EXPECT_EQ(rmdir("/set_layers_via_fds"), 0);
 }
 
 TEST_F(set_layers_via_fds, set_layers_via_fds)
@@ -266,7 +274,7 @@ TEST_F(set_layers_via_fds, set_override_creds)
 	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_STRING, "metacopy", "on", 0), 0);
 
 	pid = create_child(&pidfd, 0);
-	EXPECT_GE(pid, 0);
+	ASSERT_GE(pid, 0);
 	if (pid == 0) {
 		if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "override_creds", NULL, 0)) {
 			TH_LOG("sys_fsconfig should have succeeded");
@@ -275,11 +283,11 @@ TEST_F(set_layers_via_fds, set_override_creds)
 
 		_exit(EXIT_SUCCESS);
 	}
-	EXPECT_EQ(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
-	EXPECT_EQ(close(pidfd), 0);
+	ASSERT_GE(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
+	ASSERT_GE(close(pidfd), 0);
 
 	pid = create_child(&pidfd, 0);
-	EXPECT_GE(pid, 0);
+	ASSERT_GE(pid, 0);
 	if (pid == 0) {
 		if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "nooverride_creds", NULL, 0)) {
 			TH_LOG("sys_fsconfig should have succeeded");
@@ -288,11 +296,11 @@ TEST_F(set_layers_via_fds, set_override_creds)
 
 		_exit(EXIT_SUCCESS);
 	}
-	EXPECT_EQ(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
-	EXPECT_EQ(close(pidfd), 0);
+	ASSERT_GE(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
+	ASSERT_GE(close(pidfd), 0);
 
 	pid = create_child(&pidfd, 0);
-	EXPECT_GE(pid, 0);
+	ASSERT_GE(pid, 0);
 	if (pid == 0) {
 		if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "override_creds", NULL, 0)) {
 			TH_LOG("sys_fsconfig should have succeeded");
@@ -301,8 +309,125 @@ TEST_F(set_layers_via_fds, set_override_creds)
 
 		_exit(EXIT_SUCCESS);
 	}
-	EXPECT_EQ(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
-	EXPECT_EQ(close(pidfd), 0);
+	ASSERT_GE(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
+	ASSERT_GE(close(pidfd), 0);
+
+	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);
+
+	fd_overlay = sys_fsmount(fd_context, 0, 0);
+	ASSERT_GE(fd_overlay, 0);
+
+	ASSERT_EQ(sys_move_mount(fd_overlay, "", -EBADF, "/set_layers_via_fds", MOVE_MOUNT_F_EMPTY_PATH), 0);
+
+	ASSERT_EQ(close(fd_context), 0);
+	ASSERT_EQ(close(fd_overlay), 0);
+}
+
+TEST_F(set_layers_via_fds, set_override_creds_invalid)
+{
+	int fd_context, fd_tmpfs, fd_overlay, ret;
+	int layer_fds[] = { [0 ... 3] = -EBADF };
+	pid_t pid;
+	int fd_userns1, fd_userns2;
+	int ipc_sockets[2];
+	char c;
+	const unsigned int predictable_fd_context_nr = 123;
+
+	fd_userns1 = get_userns_fd(0, 0, 10000);
+	ASSERT_GE(fd_userns1, 0);
+
+	fd_userns2 = get_userns_fd(0, 1234, 10000);
+	ASSERT_GE(fd_userns2, 0);
+
+	ret = socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets);
+	ASSERT_GE(ret, 0);
+
+	pid = create_child(&self->pidfd, 0);
+	ASSERT_GE(pid, 0);
+	if (pid == 0) {
+		if (close(ipc_sockets[0])) {
+			TH_LOG("close should have succeeded");
+			_exit(EXIT_FAILURE);
+		}
+
+		if (!switch_userns(fd_userns2, 0, 0, false)) {
+			TH_LOG("switch_userns should have succeeded");
+			_exit(EXIT_FAILURE);
+		}
+
+		if (read_nointr(ipc_sockets[1], &c, 1) != 1) {
+			TH_LOG("read_nointr should have succeeded");
+			_exit(EXIT_FAILURE);
+		}
+
+		if (close(ipc_sockets[1])) {
+			TH_LOG("close should have succeeded");
+			_exit(EXIT_FAILURE);
+		}
+
+		if (!sys_fsconfig(predictable_fd_context_nr, FSCONFIG_SET_FLAG, "override_creds", NULL, 0)) {
+			TH_LOG("sys_fsconfig should have failed");
+			_exit(EXIT_FAILURE);
+		}
+
+		_exit(EXIT_SUCCESS);
+	}
+
+	ASSERT_EQ(close(ipc_sockets[1]), 0);
+	ASSERT_EQ(switch_userns(fd_userns1, 0, 0, false), true);
+	ASSERT_EQ(unshare(CLONE_NEWNS), 0);
+	ASSERT_EQ(sys_mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL), 0);
+
+	fd_context = sys_fsopen("tmpfs", 0);
+	ASSERT_GE(fd_context, 0);
+
+	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);
+	fd_tmpfs = sys_fsmount(fd_context, 0, 0);
+	ASSERT_GE(fd_tmpfs, 0);
+	ASSERT_EQ(close(fd_context), 0);
+
+	ASSERT_EQ(mkdirat(fd_tmpfs, "w", 0755), 0);
+	ASSERT_EQ(mkdirat(fd_tmpfs, "u", 0755), 0);
+	ASSERT_EQ(mkdirat(fd_tmpfs, "l1", 0755), 0);
+	ASSERT_EQ(mkdirat(fd_tmpfs, "l2", 0755), 0);
+
+	layer_fds[0] = openat(fd_tmpfs, "w", O_DIRECTORY);
+	ASSERT_GE(layer_fds[0], 0);
+
+	layer_fds[1] = openat(fd_tmpfs, "u", O_DIRECTORY);
+	ASSERT_GE(layer_fds[1], 0);
+
+	layer_fds[2] = openat(fd_tmpfs, "l1", O_DIRECTORY);
+	ASSERT_GE(layer_fds[2], 0);
+
+	layer_fds[3] = openat(fd_tmpfs, "l2", O_DIRECTORY);
+	ASSERT_GE(layer_fds[3], 0);
+
+	ASSERT_EQ(sys_move_mount(fd_tmpfs, "", -EBADF, "/tmp", MOVE_MOUNT_F_EMPTY_PATH), 0);
+	ASSERT_EQ(close(fd_tmpfs), 0);
+
+	fd_context = sys_fsopen("overlay", 0);
+	ASSERT_GE(fd_context, 0);
+	ASSERT_EQ(dup3(fd_context, predictable_fd_context_nr, 0), predictable_fd_context_nr);
+	ASSERT_EQ(close(fd_context), 0);
+	fd_context = predictable_fd_context_nr;
+	ASSERT_EQ(write_nointr(ipc_sockets[0], "1", 1), 1);
+	ASSERT_EQ(close(ipc_sockets[0]), 0);
+
+	ASSERT_EQ(wait_for_pid(pid), 0);
+	ASSERT_EQ(close(self->pidfd), 0);
+	self->pidfd = -EBADF;
+
+	ASSERT_NE(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir", NULL, layer_fds[2]), 0);
+	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "workdir",   NULL, layer_fds[0]), 0);
+	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "upperdir",  NULL, layer_fds[1]), 0);
+	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[2]), 0);
+	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[3]), 0);
+
+	for (int i = 0; i < ARRAY_SIZE(layer_fds); i++)
+		ASSERT_EQ(close(layer_fds[i]), 0);
+
+	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "userxattr", NULL, 0), 0);
 
 	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);
 
@@ -313,6 +438,8 @@ TEST_F(set_layers_via_fds, set_override_creds)
 
 	ASSERT_EQ(close(fd_context), 0);
 	ASSERT_EQ(close(fd_overlay), 0);
+	ASSERT_EQ(close(fd_userns1), 0);
+	ASSERT_EQ(close(fd_userns2), 0);
 }
 
 TEST_HARNESS_MAIN