syscalls: add selftest for execveat(2)

Signed-off-by: David Drysdale <drysdale@google.com>
Cc: Meredydd Luff <meredydd@senatehouse.org>
Cc: Shuah Khan <shuah.kh@samsung.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rich Felker <dalias@aerifal.cx>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Drysdale 2014-12-12 16:57:36 -08:00 committed by Linus Torvalds
parent 27d6ec7ad6
commit c9b26b81af
4 changed files with 432 additions and 0 deletions

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@ -15,6 +15,7 @@ TARGETS += user
TARGETS += sysctl
TARGETS += firmware
TARGETS += ftrace
TARGETS += exec
TARGETS_HOTPLUG = cpu-hotplug
TARGETS_HOTPLUG += memory-hotplug

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@ -0,0 +1,9 @@
subdir*
script*
execveat
execveat.symlink
execveat.moved
execveat.path.ephemeral
execveat.ephemeral
execveat.denatured
xxxxxxxx*

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@ -0,0 +1,25 @@
CC = $(CROSS_COMPILE)gcc
CFLAGS = -Wall
BINARIES = execveat
DEPS = execveat.symlink execveat.denatured script subdir
all: $(BINARIES) $(DEPS)
subdir:
mkdir -p $@
script:
echo '#!/bin/sh' > $@
echo 'exit $$*' >> $@
chmod +x $@
execveat.symlink: execveat
ln -s -f $< $@
execveat.denatured: execveat
cp $< $@
chmod -x $@
%: %.c
$(CC) $(CFLAGS) -o $@ $^
run_tests: all
./execveat
clean:
rm -rf $(BINARIES) $(DEPS) subdir.moved execveat.moved xxxxx*

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@ -0,0 +1,397 @@
/*
* 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, AT_EMPTY_PATH */
#include <sys/sendfile.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
static char longpath[2 * PATH_MAX] = "";
static char *envp[] = { "IN_TEST=yes", NULL, 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)
{
int rc;
errno = 0;
printf("Check failure of execveat(%d, '%s', %d) with %s... ",
fd, path?:"(null)", flags, errno_str);
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;
int pathlen = path ? strlen(path) : 0;
if (pathlen > 40)
printf("Check success of execveat(%d, '%.20s...%s', %d)... ",
fd, path, (path + pathlen - 20), flags);
else
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 void exe_cp(const char *src, const char *dest)
{
int in_fd = open_or_die(src, O_RDONLY);
int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755);
struct stat info;
fstat(in_fd, &info);
sendfile(out_fd, in_fd, NULL, info.st_size);
close(in_fd);
close(out_fd);
}
#define XX_DIR_LEN 200
static int check_execveat_pathmax(int dot_dfd, const char *src, int is_script)
{
int fail = 0;
int ii, count, len;
char longname[XX_DIR_LEN + 1];
int fd;
if (*longpath == '\0') {
/* Create a filename close to PATH_MAX in length */
memset(longname, 'x', XX_DIR_LEN - 1);
longname[XX_DIR_LEN - 1] = '/';
longname[XX_DIR_LEN] = '\0';
count = (PATH_MAX - 3) / XX_DIR_LEN;
for (ii = 0; ii < count; ii++) {
strcat(longpath, longname);
mkdir(longpath, 0755);
}
len = (PATH_MAX - 3) - (count * XX_DIR_LEN);
if (len <= 0)
len = 1;
memset(longname, 'y', len);
longname[len] = '\0';
strcat(longpath, longname);
}
exe_cp(src, longpath);
/*
* Execute as a pre-opened file descriptor, which works whether this is
* a script or not (because the interpreter sees a filename like
* "/dev/fd/20").
*/
fd = open(longpath, O_RDONLY);
if (fd > 0) {
printf("Invoke copy of '%s' via filename of length %lu:\n",
src, strlen(longpath));
fail += check_execveat(fd, "", AT_EMPTY_PATH);
} else {
printf("Failed to open length %lu filename, errno=%d (%s)\n",
strlen(longpath), errno, strerror(errno));
fail++;
}
/*
* Execute as a long pathname relative to ".". If this is a script,
* the interpreter will launch but fail to open the script because its
* name ("/dev/fd/5/xxx....") is bigger than PATH_MAX.
*/
if (is_script)
fail += check_execveat_invoked_rc(dot_dfd, longpath, 0, 127);
else
fail += check_execveat(dot_dfd, longpath, 0);
return fail;
}
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 dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC);
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_denatured = open_or_die("execveat.denatured", O_RDONLY);
int fd_denatured_path = open_or_die("execveat.denatured",
O_RDONLY|O_PATH);
int fd_script = open_or_die("script", O_RDONLY);
int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY);
int fd_ephemeral_path = open_or_die("execveat.path.ephemeral",
O_RDONLY|O_PATH);
int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY);
int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC);
int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC);
/* Change file position to confirm it doesn't affect anything */
lseek(fd, 10, SEEK_SET);
/* 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, "", AT_EMPTY_PATH);
/* O_CLOEXEC fd + no path */
fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH);
/* O_PATH fd */
fail += check_execveat(fd_path, "", AT_EMPTY_PATH);
/* 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, "", AT_EMPTY_PATH);
/* fd + no path to a file that's been deleted */
unlink("execveat.moved"); /* remove the file now fd open */
fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
/* Mess with executable file that's already open with O_PATH */
/* fd + no path to a file that's been deleted */
unlink("execveat.path.ephemeral");
fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH);
/* Invalid argument failures */
fail += check_execveat_fail(fd, "", 0, ENOENT);
fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT);
/* 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, "", AT_EMPTY_PATH);
fail += check_execveat(fd_symlink, "",
AT_EMPTY_PATH|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, "", AT_EMPTY_PATH);
fail += check_execveat(fd_script, "",
AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
/* O_CLOEXEC fd fails for a script (as script file inaccessible) */
fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH,
ENOENT);
fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT);
/* 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, "", AT_EMPTY_PATH);
/* fd + no path to a file that's been deleted */
unlink("script.moved"); /* remove the file while fd open */
fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
/* 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, "", AT_EMPTY_PATH, EACCES);
/* Attempt to execute non-executable => EACCES */
fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);
fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES);
fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH,
EACCES);
/* Attempt to execute nonsense FD => EBADF */
fail += check_execveat_fail(99, "", AT_EMPTY_PATH, 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);
fail += check_execveat_pathmax(dot_dfd, "execveat", 0);
fail += check_execveat_pathmax(dot_dfd, "script", 1);
return fail;
}
static void prerequisites(void)
{
int fd;
const char *script = "#!/bin/sh\nexit $*\n";
/* Create ephemeral copies of files */
exe_cp("execveat", "execveat.ephemeral");
exe_cp("execveat", "execveat.path.ephemeral");
exe_cp("script", "script.ephemeral");
mkdir("subdir.ephemeral", 0755);
fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755);
write(fd, script, strlen(script));
close(fd);
}
int main(int argc, char **argv)
{
int ii;
int rc;
const char *verbose = getenv("VERBOSE");
if (argc >= 2) {
/* If we are invoked with an argument, don't run tests. */
const char *in_test = getenv("IN_TEST");
if (verbose) {
printf(" invoked with:");
for (ii = 0; ii < argc; ii++)
printf(" [%d]='%s'", ii, argv[ii]);
printf("\n");
}
/* Check expected environment transferred. */
if (!in_test || strcmp(in_test, "yes") != 0) {
printf("[FAIL] (no IN_TEST=yes in env)\n");
return 1;
}
/* Use the final argument as an exit code. */
rc = atoi(argv[argc - 1]);
fflush(stdout);
} else {
prerequisites();
if (verbose)
envp[1] = "VERBOSE=1";
rc = run_tests();
if (rc > 0)
printf("%d tests failed\n", rc);
}
return rc;
}