[PATCHv4 RESEND 2/3] syscalls,x86: add selftest for execveat(2)

[David Drysdale <drysdale@google.com>]

Signed-off-by: David Drysdale <drysdale@google.com>
---
 tools/testing/selftests/Makefile        |   1 +
 tools/testing/selftests/exec/.gitignore |   6 +
 tools/testing/selftests/exec/Makefile   |  32 ++++
 tools/testing/selftests/exec/execveat.c | 251 ++++++++++++++++++++++++++++++++
 4 files changed, 290 insertions(+)
 create mode 100644 tools/testing/selftests/exec/.gitignore
 create mode 100644 tools/testing/selftests/exec/Makefile
 create mode 100644 tools/testing/selftests/exec/execveat.c

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 32487ed18354..26b7e6410fcd 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -10,6 +10,7 @@ TARGETS += timers
 TARGETS += vm
 TARGETS += powerpc
 TARGETS += user
+TARGETS += exec

 all:
 	for TARGET in $(TARGETS); do \
diff --git a/tools/testing/selftests/exec/.gitignore b/tools/testing/selftests/exec/.gitignore
new file mode 100644
index 000000000000..349a786899a7
--- /dev/null
+++ b/tools/testing/selftests/exec/.gitignore
@@ -0,0 +1,6 @@
+subdir*
+script*
+execveat
+execveat.symlink
+execveat.moved
+execveat.ephemeral
diff --git a/tools/testing/selftests/exec/Makefile b/tools/testing/selftests/exec/Makefile
new file mode 100644
index 000000000000..55771ed05dda
--- /dev/null
+++ b/tools/testing/selftests/exec/Makefile
@@ -0,0 +1,32 @@
+CC = $(CROSS_COMPILE)gcc
+CFLAGS = -Wall
+BINARIES = execveat
+DEPS = execveat.symlink script execveat.ephemeral script.ephemeral subdir subdir.ephemeral subdir.ephemeral/script
+all: $(BINARIES) $(DEPS)
+
+subdir:
+	mkdir -p $@
+subdir.ephemeral:
+	mkdir -p $@
+subdir.ephemeral/script: | subdir.ephemeral
+	echo '#!/bin/sh' > $@
+	echo 'exit $$*' >> $@
+	chmod +x $@
+script:
+	echo '#!/bin/sh' > $@
+	echo 'exit $$*' >> $@
+	chmod +x $@
+script.ephemeral: script
+	cp $< $@
+execveat.symlink: execveat
+	ln -s -f $< $@
+execveat.ephemeral: execveat
+	cp $< $@
+%: %.c
+	$(CC) $(CFLAGS) -o $@ $^
+
+run_tests: all
+	./execveat
+
+clean:
+	rm -rf $(BINARIES) $(DEPS) subdir.moved execveat.moved
diff --git a/tools/testing/selftests/exec/execveat.c b/tools/testing/selftests/exec/execveat.c
new file mode 100644
index 000000000000..f67862fa3f38
--- /dev/null
+++ b/tools/testing/selftests/exec/execveat.c
@@ -0,0 +1,251 @@
+/*
+ * Copyright (c) 2014 Google, Inc.
+ *
+ * Licensed under the terms of the GNU GPL License version 2
+ *
+ * Selftests for execveat(2).
+ */
+
+#define _GNU_SOURCE  /* to get O_PATH */
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/syscall.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <limits.h>
+#include <stdlib.h>
+
+static char *envp[] = { "IN_TEST=yes", NULL };
+static char *argv[] = { "execveat", "99", NULL };
+
+static int execveat_(int fd, const char *path, char **argv, char **envp,
+		     int flags)
+{
+#ifdef __NR_execveat
+	return syscall(__NR_execveat, fd, path, argv, envp, flags);
+#else
+	errno = -ENOSYS;
+	return -1;
+#endif
+}
+
+#define check_execveat_fail(fd, path, flags, errno)	\
+	_check_execveat_fail(fd, path, flags, errno, #errno)
+static int _check_execveat_fail(int fd, const char *path, int flags,
+				int expected_errno, const char *errno_str)
+{
+	errno = 0;
+	printf("Check failure of execveat(%d, '%s', %d) with %s... ",
+		fd, path?:"(null)", flags, errno_str);
+	int rc = execveat_(fd, path, argv, envp, flags);
+	if (rc > 0) {
+		printf("[FAIL] (unexpected success from execveat(2))\n");
+		return 1;
+	}
+	if (errno != expected_errno) {
+		printf("[FAIL] (expected errno %d (%s) not %d (%s)\n",
+			expected_errno, strerror(expected_errno),
+			errno, strerror(errno));
+		return 1;
+	}
+	printf("[OK]\n");
+	return 0;
+}
+
+static int check_execveat_invoked_rc(int fd, const char *path, int flags,
+				     int expected_rc)
+{
+	int status;
+	int rc;
+	pid_t child;
+	printf("Check success of execveat(%d, '%s', %d)... ",
+		fd, path?:"(null)", flags);
+	child = fork();
+	if (child < 0) {
+		printf("[FAIL] (fork() failed)\n");
+		return 1;
+	}
+	if (child == 0) {
+		/* Child: do execveat(). */
+		rc = execveat_(fd, path, argv, envp, flags);
+		printf("[FAIL]: execveat() failed, rc=%d errno=%d (%s)\n",
+			rc, errno, strerror(errno));
+		exit(1);  /* should not reach here */
+	}
+	/* Parent: wait for & check child's exit status. */
+	rc = waitpid(child, &status, 0);
+	if (rc != child) {
+		printf("[FAIL] (waitpid(%d,...) returned %d)\n", child, rc);
+		return 1;
+	}
+	if (!WIFEXITED(status)) {
+		printf("[FAIL] (child %d did not exit cleanly, status=%08x)\n",
+			child, status);
+		return 1;
+	}
+	if (WEXITSTATUS(status) != expected_rc) {
+		printf("[FAIL] (child %d exited with %d not %d)\n",
+			child, WEXITSTATUS(status), expected_rc);
+		return 1;
+	}
+	printf("[OK]\n");
+	return 0;
+}
+
+static int check_execveat(int fd, const char *path, int flags)
+{
+	return check_execveat_invoked_rc(fd, path, flags, 99);
+}
+
+static char *concat(const char *left, const char *right)
+{
+	char *result = malloc(strlen(left) + strlen(right) + 1);
+	strcpy(result, left);
+	strcat(result, right);
+	return result;
+}
+
+static int open_or_die(const char *filename, int flags)
+{
+	int fd = open(filename, flags);
+	if (fd < 0) {
+		printf("Failed to open '%s'; "
+			"check prerequisites are available\n", filename);
+		exit(1);
+	}
+	return fd;
+}
+
+static int run_tests(void)
+{
+	int fail = 0;
+	char *fullname = realpath("execveat", NULL);
+	char *fullname_script = realpath("script", NULL);
+	char *fullname_symlink = concat(fullname, ".symlink");
+	int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY);
+	int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral",
+					       O_DIRECTORY|O_RDONLY);
+	int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY);
+	int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH);
+	int fd = open_or_die("execveat", O_RDONLY);
+	int fd_path = open_or_die("execveat", O_RDONLY|O_PATH);
+	int fd_symlink = open_or_die("execveat.symlink", O_RDONLY);
+	int fd_script = open_or_die("script", O_RDONLY);
+	int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY);
+	int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY);
+
+	/* Normal executable file: */
+	/*   dfd + path */
+	fail |= check_execveat(subdir_dfd, "../execveat", 0);
+	fail |= check_execveat(dot_dfd, "execveat", 0);
+	fail |= check_execveat(dot_dfd_path, "execveat", 0);
+	/*   absolute path */
+	fail |= check_execveat(AT_FDCWD, fullname, 0);
+	/*   absolute path with nonsense dfd */
+	fail |= check_execveat(99, fullname, 0);
+	/*   fd + no path */
+	fail |= check_execveat(fd, NULL, 0);
+
+	/* Mess with executable file that's already open: */
+	/*   fd + no path to a file that's been renamed */
+	rename("execveat.ephemeral", "execveat.moved");
+	fail |= check_execveat(fd_ephemeral, NULL, 0);
+	/*   fd + no path to a file that's been deleted */
+	unlink("execveat.moved"); /* remove the file now fd open */
+	fail |= check_execveat(fd_ephemeral, NULL, 0);
+
+	/* Symlink to executable file: */
+	/*   dfd + path */
+	fail |= check_execveat(dot_dfd, "execveat.symlink", 0);
+	fail |= check_execveat(dot_dfd_path, "execveat.symlink", 0);
+	/*   absolute path */
+	fail |= check_execveat(AT_FDCWD, fullname_symlink, 0);
+	/*   fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */
+	fail |= check_execveat(fd_symlink, NULL, 0);
+	fail |= check_execveat(fd_symlink, NULL, AT_SYMLINK_NOFOLLOW);
+
+	/* Symlink fails when AT_SYMLINK_NOFOLLOW set: */
+	/*   dfd + path */
+	fail |= check_execveat_fail(dot_dfd, "execveat.symlink",
+				    AT_SYMLINK_NOFOLLOW, ELOOP);
+	fail |= check_execveat_fail(dot_dfd_path, "execveat.symlink",
+				    AT_SYMLINK_NOFOLLOW, ELOOP);
+	/*   absolute path */
+	fail |= check_execveat_fail(AT_FDCWD, fullname_symlink,
+				    AT_SYMLINK_NOFOLLOW, ELOOP);
+
+	/* Shell script wrapping executable file: */
+	/*   dfd + path */
+	fail |= check_execveat(subdir_dfd, "../script", 0);
+	fail |= check_execveat(dot_dfd, "script", 0);
+	fail |= check_execveat(dot_dfd_path, "script", 0);
+	/*   absolute path */
+	fail |= check_execveat(AT_FDCWD, fullname_script, 0);
+	/*   fd + no path */
+	fail |= check_execveat(fd_script, NULL, 0);
+	fail |= check_execveat(fd_script, NULL, AT_SYMLINK_NOFOLLOW);
+
+	/* Mess with script file that's already open: */
+	/*   fd + no path to a file that's been renamed */
+	rename("script.ephemeral", "script.moved");
+	fail |= check_execveat(fd_script_ephemeral, NULL, 0);
+	/*   fd + no path to a file that's been deleted */
+	unlink("script.moved"); /* remove the file while fd open */
+	/* Shell attempts to load the deleted file but fails => rc=127 */
+	fail |= check_execveat_invoked_rc(fd_script_ephemeral, NULL, 0, 127);
+
+	/* Rename a subdirectory in the path: */
+	rename("subdir.ephemeral", "subdir.moved");
+	fail |= check_execveat(subdir_dfd_ephemeral, "../script", 0);
+	fail |= check_execveat(subdir_dfd_ephemeral, "script", 0);
+	/* Remove the subdir and its contents */
+	unlink("subdir.moved/script");
+	unlink("subdir.moved");
+	/* Shell loads via deleted subdir OK because name starts with .. */
+	fail |= check_execveat(subdir_dfd_ephemeral, "../script", 0);
+	fail |= check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT);
+
+	/* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */
+	fail |= check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL);
+	/* Invalid path => ENOENT */
+	fail |= check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT);
+	fail |= check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT);
+	fail |= check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT);
+	/* Attempt to execute directory => EACCES */
+	fail |= check_execveat_fail(dot_dfd, NULL, 0, EACCES);
+	/* Attempt to execute non-executable => EACCES */
+	fail |= check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);
+	/* Attempt to execute file opened with O_PATH => EBADF */
+	fail |= check_execveat_fail(dot_dfd_path, NULL, 0, EBADF);
+	fail |= check_execveat_fail(fd_path, NULL, 0, EBADF);
+	/* Attempt to execute nonsense FD => EBADF */
+	fail |= check_execveat_fail(99, NULL, 0, EBADF);
+	fail |= check_execveat_fail(99, "execveat", 0, EBADF);
+	/* Attempt to execute relative to non-directory => ENOTDIR */
+	fail |= check_execveat_fail(fd, "execveat", 0, ENOTDIR);
+
+	return fail ? -1 : 0;
+}
+
+int main(int argc, char **argv)
+{
+	if (argc >= 2) {
+		/* If we are invoked with an argument, exit immediately. */
+		/* Check expected environment transferred. */
+		if (strcmp(getenv("IN_TEST"), "yes") != 0) {
+			printf("[FAIL] (no IN_TEST=yes in env)\n");
+			return 1;
+		}
+
+		/* Use the argument as an exit code. */
+		int rc = atoi(argv[1]);
+		fflush(stdout);
+		return rc;
+	} else {
+		return run_tests();
+	}
+}
--
1.9.1.423.g4596e3a