Commit 32d118ad authored by Daniel Verkamp's avatar Daniel Verkamp Committed by Andrew Morton
Browse files

selftests/memfd: add tests for F_SEAL_EXEC 

Basic tests to ensure that user/group/other execute bits cannot be changed
after applying F_SEAL_EXEC to a memfd.

Link: https://lkml.kernel.org/r/20221215001205.51969-3-jeffxu@google.com


Signed-off-by: default avatarDaniel Verkamp <dverkamp@chromium.org>
Co-developed-by: default avatarJeff Xu <jeffxu@google.com>
Signed-off-by: default avatarJeff Xu <jeffxu@google.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cc: kernel test robot <lkp@intel.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 6fd73538

tools/testing/selftests/memfd/memfd_test.c

+122 −1
Original line number Diff line number Diff line
@@ -28,12 +28,38 @@ 
#define MFD_DEF_SIZE 8192

#define STACK_SIZE 65536



#define F_SEAL_EXEC	0x0020



/*

 * Default is not to test hugetlbfs

 */

static size_t mfd_def_size = MFD_DEF_SIZE;

static const char *memfd_str = MEMFD_STR;



static ssize_t fd2name(int fd, char *buf, size_t bufsize)

{

	char buf1[PATH_MAX];

	int size;

	ssize_t nbytes;



	size = snprintf(buf1, PATH_MAX, "/proc/self/fd/%d", fd);

	if (size < 0) {

		printf("snprintf(%d) failed on %m\n", fd);

		abort();

	}



	/*

	 * reserver one byte for string termination.

	 */

	nbytes = readlink(buf1, buf, bufsize-1);

	if (nbytes == -1) {

		printf("readlink(%s) failed %m\n", buf1);

		abort();

	}

	buf[nbytes] = '\0';

	return nbytes;

}



static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)

{

	int r, fd;
@@ -98,11 +124,14 @@ static unsigned int mfd_assert_get_seals(int fd) 


static void mfd_assert_has_seals(int fd, unsigned int seals)

{

	char buf[PATH_MAX];

	int nbytes;

	unsigned int s;

	fd2name(fd, buf, PATH_MAX);



	s = mfd_assert_get_seals(fd);

	if (s != seals) {

		printf("%u != %u = GET_SEALS(%d)\n", seals, s, fd);

		printf("%u != %u = GET_SEALS(%s)\n", seals, s, buf);

		abort();

	}

}
@@ -594,6 +623,64 @@ static void mfd_fail_grow_write(int fd) 
	}

}



static void mfd_assert_mode(int fd, int mode)

{

	struct stat st;

	char buf[PATH_MAX];

	int nbytes;



	fd2name(fd, buf, PATH_MAX);



	if (fstat(fd, &st) < 0) {

		printf("fstat(%s) failed: %m\n", buf);

		abort();

	}



	if ((st.st_mode & 07777) != mode) {

		printf("fstat(%s) wrong file mode 0%04o, but expected 0%04o\n",

		       buf, (int)st.st_mode & 07777, mode);

		abort();

	}

}



static void mfd_assert_chmod(int fd, int mode)

{

	char buf[PATH_MAX];

	int nbytes;



	fd2name(fd, buf, PATH_MAX);



	if (fchmod(fd, mode) < 0) {

		printf("fchmod(%s, 0%04o) failed: %m\n", buf, mode);

		abort();

	}



	mfd_assert_mode(fd, mode);

}



static void mfd_fail_chmod(int fd, int mode)

{

	struct stat st;

	char buf[PATH_MAX];

	int nbytes;



	fd2name(fd, buf, PATH_MAX);



	if (fstat(fd, &st) < 0) {

		printf("fstat(%s) failed: %m\n", buf);

		abort();

	}



	if (fchmod(fd, mode) == 0) {

		printf("fchmod(%s, 0%04o) didn't fail as expected\n",

		       buf, mode);

		abort();

	}



	/* verify that file mode bits did not change */

	mfd_assert_mode(fd, st.st_mode & 07777);

}



static int idle_thread_fn(void *arg)

{

	sigset_t set;
@@ -880,6 +967,39 @@ static void test_seal_resize(void) 
	close(fd);

}



/*

 * Test SEAL_EXEC

 * Test that chmod() cannot change x bits after sealing

 */

static void test_seal_exec(void)

{

	int fd;



	printf("%s SEAL-EXEC\n", memfd_str);



	fd = mfd_assert_new("kern_memfd_seal_exec",

			    mfd_def_size,

			    MFD_CLOEXEC | MFD_ALLOW_SEALING);



	mfd_assert_mode(fd, 0777);



	mfd_assert_chmod(fd, 0644);



	mfd_assert_has_seals(fd, 0);

	mfd_assert_add_seals(fd, F_SEAL_EXEC);

	mfd_assert_has_seals(fd, F_SEAL_EXEC);



	mfd_assert_chmod(fd, 0600);

	mfd_fail_chmod(fd, 0777);

	mfd_fail_chmod(fd, 0670);

	mfd_fail_chmod(fd, 0605);

	mfd_fail_chmod(fd, 0700);

	mfd_fail_chmod(fd, 0100);

	mfd_assert_chmod(fd, 0666);



	close(fd);

}



/*

 * Test sharing via dup()

 * Test that seals are shared between dupped FDs and they're all equal.
@@ -1059,6 +1179,7 @@ int main(int argc, char **argv) 
	test_seal_shrink();

	test_seal_grow();

	test_seal_resize();

	test_seal_exec();



	test_share_dup("SHARE-DUP", "");

	test_share_mmap("SHARE-MMAP", "");