Re: [PATCH v2 3/3] selftests: add memfd_create() + sealing tests

[Hugh Dickins]

On Tue, 15 Apr 2014, David Herrmann wrote:

> Some basic tests to verify sealing on memfds works as expected and
> guarantees the advertised semantics.

Thanks for providing these.

A few remarks below, and I should note one oddity.

Curious about leaks (probably none, I was merely curious), I tried to
run memfd_test 4096 times in succession, and never succeeded.  After
many iterations, the 32-bit one tends to hang somewhere just before
reaching the DONE, and the 64-bit one gave me some kind of assert
error from a library.

I expect there's some threading race around join_idle_thread():
which I think you will sort out infinitely sooner than I would.
No need to fix it right now: the test works well enough.

> 
> Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
> ---
>  tools/testing/selftests/Makefile           |   1 +
>  tools/testing/selftests/memfd/.gitignore   |   2 +
>  tools/testing/selftests/memfd/Makefile     |  29 +
>  tools/testing/selftests/memfd/memfd_test.c | 944 +++++++++++++++++++++++++++++
>  4 files changed, 976 insertions(+)
>  create mode 100644 tools/testing/selftests/memfd/.gitignore
>  create mode 100644 tools/testing/selftests/memfd/Makefile
>  create mode 100644 tools/testing/selftests/memfd/memfd_test.c
> 
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index 32487ed..c57325a 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -2,6 +2,7 @@ TARGETS = breakpoints
>  TARGETS += cpu-hotplug
>  TARGETS += efivarfs
>  TARGETS += kcmp
> +TARGETS += memfd
>  TARGETS += memory-hotplug
>  TARGETS += mqueue
>  TARGETS += net
> diff --git a/tools/testing/selftests/memfd/.gitignore b/tools/testing/selftests/memfd/.gitignore
> new file mode 100644
> index 0000000..bcc8ee2
> --- /dev/null
> +++ b/tools/testing/selftests/memfd/.gitignore
> @@ -0,0 +1,2 @@
> +memfd_test
> +memfd-test-file
> diff --git a/tools/testing/selftests/memfd/Makefile b/tools/testing/selftests/memfd/Makefile
> new file mode 100644
> index 0000000..36653b9
> --- /dev/null
> +++ b/tools/testing/selftests/memfd/Makefile
> @@ -0,0 +1,29 @@
> +uname_M := $(shell uname -m 2>/dev/null || echo not)
> +ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/i386/)
> +ifeq ($(ARCH),i386)
> +	ARCH := X86
> +endif
> +ifeq ($(ARCH),x86_64)
> +	ARCH := X86
> +endif
> +
> +CFLAGS += -I../../../../arch/x86/include/generated/uapi/
> +CFLAGS += -I../../../../arch/x86/include/uapi/
> +CFLAGS += -I../../../../include/uapi/
> +CFLAGS += -I../../../../include/
> +
> +all:
> +ifeq ($(ARCH),X86)
> +	gcc $(CFLAGS) memfd_test.c -o memfd_test
> +else
> +	echo "Not an x86 target, can't build memfd selftest"
> +endif
> +
> +run_tests: all
> +ifeq ($(ARCH),X86)
> +	gcc $(CFLAGS) memfd_test.c -o memfd_test
> +endif
> +	@./memfd_test || echo "memfd_test: [FAIL]"
> +
> +clean:
> +	$(RM) memfd_test
> diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
> new file mode 100644
> index 0000000..3e105ea
> --- /dev/null
> +++ b/tools/testing/selftests/memfd/memfd_test.c
> @@ -0,0 +1,944 @@
> +#define _GNU_SOURCE
> +#define __EXPORTED_HEADERS__
> +
> +#include <errno.h>
> +#include <inttypes.h>
> +#include <limits.h>
> +#include <linux/falloc.h>
> +#include <linux/fcntl.h>
> +#include <linux/memfd.h>
> +#include <sched.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <signal.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/syscall.h>
> +#include <unistd.h>
> +
> +#define MFD_DEF_SIZE 8192
> +#define STACK_SIZE 65535
> +
> +static int sys_memfd_create(const char *name,
> +			    __u64 size,
> +			    __u64 flags)
> +{
> +	return syscall(__NR_memfd_create, name, size, flags);
> +}
> +
> +static int mfd_assert_new(const char *name, __u64 sz, __u64 flags)
> +{
> +	int r;
> +
> +	r = sys_memfd_create(name, sz, flags);
> +	if (r < 0) {
> +		printf("memfd_create(\"%s\", %llu, %llu) failed: %m\n",
> +		       name,
> +		       (unsigned long long)sz,
> +		       (unsigned long long)flags);
> +		abort();
> +	}
> +
> +	return r;
> +}
> +
> +static void mfd_fail_new(const char *name, __u64 size, __u64 flags)
> +{
> +	int r;
> +
> +	r = sys_memfd_create(name, size, flags);
> +	if (r >= 0) {
> +		printf("memfd_create(\"%s\", %llu, %llu) succeeded, but failure expected\n",

scripts/checkpatch.pl complains about line-length: please ignore it on this.

> +		       name,
> +		       (unsigned long long)size,
> +		       (unsigned long long)flags);
> +		close(r);
> +		abort();
> +	}
> +}
> +
> +static __u64 mfd_assert_get_seals(int fd)
> +{
> +	long r;
> +
> +	r = fcntl(fd, F_GET_SEALS);
> +	if (r < 0) {
> +		printf("GET_SEALS(%d) failed: %m\n", fd);
> +		abort();
> +	}
> +
> +	return r;
> +}
> +
> +static void mfd_fail_get_seals(int fd)
> +{
> +	long r;
> +
> +	r = fcntl(fd, F_GET_SEALS);
> +	if (r >= 0) {
> +		printf("GET_SEALS(%d) succeeded, but failure expected\n");
> +		abort();
> +	}
> +}
> +
> +static void mfd_assert_has_seals(int fd, __u64 seals)
> +{
> +	__u64 s;
> +
> +	s = mfd_assert_get_seals(fd);
> +	if (s != seals) {
> +		printf("%llu != %llu = GET_SEALS(%d)\n",
> +		       (unsigned long long)seals, (unsigned long long)s, fd);
> +		abort();
> +	}
> +}
> +
> +static void mfd_assert_add_seals(int fd, __u64 seals)
> +{
> +	long r;
> +	__u64 s;
> +
> +	s = mfd_assert_get_seals(fd);
> +	r = fcntl(fd, F_ADD_SEALS, seals);
> +	if (r < 0) {
> +		printf("ADD_SEALS(%d, %llu -> %llu) failed: %m\n",
> +		       fd, (unsigned long long)s, (unsigned long long)seals);
> +		abort();
> +	}
> +}
> +
> +static void mfd_fail_add_seals(int fd, __u64 seals)
> +{
> +	long r;
> +	__u64 s;
> +
> +	r = fcntl(fd, F_GET_SEALS);
> +	if (r < 0)
> +		s = 0;
> +	else
> +		s = r;
> +
> +	r = fcntl(fd, F_ADD_SEALS, seals);
> +	if (r >= 0) {
> +		printf("ADD_SEALS(%d, %llu -> %llu) didn't fail as expected\n",
> +		       fd, (unsigned long long)s, (unsigned long long)seals);
> +		abort();
> +	}
> +}
> +
> +static void mfd_assert_size(int fd, size_t size)
> +{
> +	struct stat st;
> +	int r;
> +
> +	r = fstat(fd, &st);
> +	if (r < 0) {
> +		printf("fstat(%d) failed: %m\n", fd);
> +		abort();
> +	} else if (st.st_size != size) {
> +		printf("wrong file size %lld, but expected %lld\n",
> +		       (long long)st.st_size, (long long)size);
> +		abort();
> +	}
> +}
> +
> +static int mfd_assert_dup(int fd)
> +{
> +	int r;
> +
> +	r = dup(fd);
> +	if (r < 0) {
> +		printf("dup(%d) failed: %m\n", fd);
> +		abort();
> +	}
> +
> +	return r;
> +}
> +
> +static void *mfd_assert_mmap_shared(int fd)
> +{
> +	void *p;
> +
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ | PROT_WRITE,
> +		 MAP_SHARED,
> +		 fd,
> +		 0);
> +	if (p == MAP_FAILED) {
> +		printf("mmap() failed: %m\n");
> +		abort();
> +	}
> +
> +	return p;
> +}
> +
> +static void *mfd_assert_mmap_private(int fd)
> +{
> +	void *p;
> +
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ,
> +		 MAP_PRIVATE,
> +		 fd,
> +		 0);
> +	if (p == MAP_FAILED) {
> +		printf("mmap() failed: %m\n");
> +		abort();
> +	}
> +
> +	return p;
> +}
> +
> +static int mfd_assert_open(int fd, int flags, mode_t mode)
> +{
> +	char buf[512];
> +	int r;
> +
> +	sprintf(buf, "/proc/self/fd/%d", fd);
> +	r = open(buf, flags, mode);
> +	if (r < 0) {
> +		printf("open(%s) failed: %m\n", buf);
> +		abort();
> +	}
> +
> +	return r;
> +}
> +
> +static void mfd_fail_open(int fd, int flags, mode_t mode)
> +{
> +	char buf[512];
> +	int r;
> +
> +	sprintf(buf, "/proc/self/fd/%d", fd);
> +	r = open(buf, flags, mode);
> +	if (r >= 0) {
> +		printf("open(%s) didn't fail as expected\n");
> +		abort();
> +	}
> +}
> +
> +static void mfd_assert_read(int fd)
> +{
> +	char buf[16];
> +	void *p;
> +	ssize_t l;
> +
> +	l = read(fd, buf, sizeof(buf));
> +	if (l != sizeof(buf)) {
> +		printf("read() failed: %m\n");
> +		abort();
> +	}
> +
> +	/* verify PROT_READ *is* allowed */
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ,
> +		 MAP_PRIVATE,
> +		 fd,
> +		 0);
> +	if (p == MAP_FAILED) {
> +		printf("mmap() failed: %m\n");
> +		abort();
> +	}
> +	munmap(p, MFD_DEF_SIZE);
> +
> +	/* verify MAP_PRIVATE is *always* allowed (even writable) */
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ | PROT_WRITE,
> +		 MAP_PRIVATE,
> +		 fd,
> +		 0);
> +	if (p == MAP_FAILED) {
> +		printf("mmap() failed: %m\n");
> +		abort();
> +	}
> +	munmap(p, MFD_DEF_SIZE);
> +}
> +
> +static void mfd_assert_write(int fd)
> +{
> +	ssize_t l;
> +	void *p;
> +	int r;
> +
> +	/* verify write() succeeds */
> +	l = write(fd, "\0\0\0\0", 4);
> +	if (l != 4) {
> +		printf("write() failed: %m\n");
> +		abort();
> +	}
> +
> +	/* verify PROT_READ | PROT_WRITE is allowed */
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ | PROT_WRITE,
> +		 MAP_SHARED,
> +		 fd,
> +		 0);
> +	if (p == MAP_FAILED) {
> +		printf("mmap() failed: %m\n");
> +		abort();
> +	}
> +	*(char*)p = 0;

scripts/checkpatch.pl complains about (char*): better calm it with (char *).
Same on two other lines below.

> +	munmap(p, MFD_DEF_SIZE);
> +
> +	/* verify PROT_WRITE is allowed */
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_WRITE,
> +		 MAP_SHARED,
> +		 fd,
> +		 0);
> +	if (p == MAP_FAILED) {
> +		printf("mmap() failed: %m\n");
> +		abort();
> +	}
> +	*(char*)p = 0;
> +	munmap(p, MFD_DEF_SIZE);
> +
> +	/* verify PROT_READ with MAP_SHARED is allowed and a following
> +	 * mprotect(PROT_WRITE) allows writing */
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ,
> +		 MAP_SHARED,
> +		 fd,
> +		 0);
> +	if (p == MAP_FAILED) {
> +		printf("mmap() failed: %m\n");
> +		abort();
> +	}
> +
> +	r = mprotect(p, MFD_DEF_SIZE, PROT_READ | PROT_WRITE);
> +	if (r < 0) {
> +		printf("mprotect() failed: %m\n");
> +		abort();
> +	}
> +
> +	*(char*)p = 0;
> +	munmap(p, MFD_DEF_SIZE);
> +
> +	/* verify PUNCH_HOLE works */
> +	r = fallocate(fd,
> +		      FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> +		      0,
> +		      MFD_DEF_SIZE);
> +	if (r < 0) {
> +		printf("fallocate(PUNCH_HOLE) failed: %m\n");
> +		abort();
> +	}
> +}
> +
> +static void mfd_fail_write(int fd)
> +{
> +	ssize_t l;
> +	void *p;
> +	int r;
> +
> +	/* verify write() fails */
> +	l = write(fd, "data", 4);
> +	if (l != -EPERM) {
> +		printf("expected EPERM on write(), but got %d: %m\n", (int)l);
> +		abort();
> +	}
> +
> +	/* verify PROT_READ | PROT_WRITE is not allowed */
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ | PROT_WRITE,
> +		 MAP_SHARED,
> +		 fd,
> +		 0);
> +	if (p != MAP_FAILED) {
> +		printf("mmap() didn't fail as expected\n");
> +		abort();
> +	}
> +
> +	/* verify PROT_WRITE is not allowed */
> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_WRITE,
> +		 MAP_SHARED,
> +		 fd,
> +		 0);
> +	if (p != MAP_FAILED) {
> +		printf("mmap() didn't fail as expected\n");
> +		abort();
> +	}
> +
> +	/* verify PROT_READ with MAP_SHARED is not allowed */

This is a particularly interesting case, checking PROT_READ,MAP_SHARED
not allowed in mfd_fail_write().  It feels invidious to ask for more
of a comment, in a test which you have been generous to provide at all.
But it stopped me short for a while: more comment might help others too.

The reason being (right?) that this fd was opened O_RDWR, so a
MAP_SHARED mapping would permit a subsequent mprotect(,,PROT_WRITE),
which sealing the file against writes must prevent.

Your kernel checks rely on VM_SHARED and i_mmap_writable for this
protection: which is fine, but an implementation detail which could
be modified in future, if this case were ever to pose a difficulty.

> +	p = mmap(NULL,
> +		 MFD_DEF_SIZE,
> +		 PROT_READ,
> +		 MAP_SHARED,
> +		 fd,
> +		 0);
> +	if (p != MAP_FAILED) {
> +		printf("mmap() didn't fail as expected\n");
> +		abort();
> +	}
> +
> +	/* verify PUNCH_HOLE fails */
> +	r = fallocate(fd,
> +		      FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> +		      0,
> +		      MFD_DEF_SIZE);
> +	if (r >= 0) {
> +		printf("fallocate(PUNCH_HOLE) didn't fail as expected\n");
> +		abort();
> +	}
> +}
> +
> +static void mfd_assert_shrink(int fd)
> +{
> +	int r, fd2;
> +
> +	r = ftruncate(fd, MFD_DEF_SIZE / 2);
> +	if (r < 0) {
> +		printf("ftruncate(SHRINK) failed: %m\n");
> +		abort();
> +	}
> +
> +	mfd_assert_size(fd, MFD_DEF_SIZE / 2);
> +
> +	fd2 = mfd_assert_open(fd,
> +			      O_RDWR | O_CREAT | O_TRUNC,
> +			      S_IRUSR | S_IWUSR);
> +	close(fd2);
> +
> +	mfd_assert_size(fd, 0);
> +}
> +
> +static void mfd_fail_shrink(int fd)
> +{
> +	int r;
> +
> +	r = ftruncate(fd, MFD_DEF_SIZE / 2);
> +	if (r >= 0) {
> +		printf("ftruncate(SHRINK) didn't fail as expected\n");
> +		abort();
> +	}
> +
> +	mfd_fail_open(fd,
> +		      O_RDWR | O_CREAT | O_TRUNC,
> +		      S_IRUSR | S_IWUSR);
> +}
> +
> +static void mfd_assert_grow(int fd)
> +{
> +	int r;
> +
> +	r = ftruncate(fd, MFD_DEF_SIZE * 2);
> +	if (r < 0) {
> +		printf("ftruncate(GROW) failed: %m\n");
> +		abort();
> +	}
> +
> +	mfd_assert_size(fd, MFD_DEF_SIZE * 2);
> +
> +	r = fallocate(fd,
> +		      0,
> +		      0,
> +		      MFD_DEF_SIZE * 4);
> +	if (r < 0) {
> +		printf("fallocate(ALLOC) failed: %m\n");
> +		abort();
> +	}
> +
> +	mfd_assert_size(fd, MFD_DEF_SIZE * 4);
> +}
> +
> +static void mfd_fail_grow(int fd)
> +{
> +	int r;
> +
> +	r = ftruncate(fd, MFD_DEF_SIZE * 2);
> +	if (r >= 0) {
> +		printf("ftruncate(GROW) didn't fail as expected\n");
> +		abort();
> +	}
> +
> +	r = fallocate(fd,
> +		      0,
> +		      0,
> +		      MFD_DEF_SIZE * 4);
> +	if (r >= 0) {
> +		printf("fallocate(ALLOC) didn't fail as expected\n");
> +		abort();
> +	}
> +}
> +
> +static void mfd_assert_grow_write(int fd)
> +{
> +	static char buf[MFD_DEF_SIZE * 8];
> +	ssize_t l;
> +
> +	l = pwrite(fd, buf, sizeof(buf), 0);
> +	if (l != sizeof(buf)) {
> +		printf("pwrite() failed: %m\n");
> +		abort();
> +	}
> +
> +	mfd_assert_size(fd, MFD_DEF_SIZE * 8);
> +}
> +
> +static void mfd_fail_grow_write(int fd)
> +{
> +	static char buf[MFD_DEF_SIZE * 8];
> +	ssize_t l;
> +
> +	l = pwrite(fd, buf, sizeof(buf), 0);
> +	if (l == sizeof(buf)) {
> +		printf("pwrite() didn't fail as expected\n");
> +		abort();
> +	}
> +}
> +
> +static int idle_thread_fn(void *arg)
> +{
> +	sigset_t set;
> +	int sig;
> +
> +	/* dummy waiter; SIGTERM terminates us anyway */
> +	sigemptyset(&set);
> +	sigaddset(&set, SIGTERM);
> +	sigwait(&set, &sig);
> +
> +	return 0;
> +}
> +
> +static pid_t spawn_idle_thread(void)
> +{
> +	uint8_t *stack;
> +	pid_t pid;
> +
> +	stack = malloc(STACK_SIZE);
> +	if (!stack) {
> +		printf("malloc(STACK_SIZE) failed: %m\n");
> +		abort();
> +	}
> +
> +	pid = clone(idle_thread_fn,
> +		    stack + STACK_SIZE,
> +		    CLONE_FILES | CLONE_FS | CLONE_VM | SIGCHLD,
> +		    NULL);
> +	if (pid < 0) {
> +		printf("clone() failed: %m\n");
> +		abort();
> +	}
> +
> +	return pid;
> +}
> +
> +static void join_idle_thread(pid_t pid)
> +{
> +	kill(pid, SIGTERM);
> +	waitpid(pid, NULL, 0);
> +}
> +
> +static pid_t spawn_idle_proc(void)
> +{
> +	pid_t pid;
> +	sigset_t set;
> +	int sig;
> +
> +	pid = fork();
> +	if (pid < 0) {
> +		printf("fork() failed: %m\n");
> +		abort();
> +	} else if (!pid) {
> +		/* dummy waiter; SIGTERM terminates us anyway */
> +		sigemptyset(&set);
> +		sigaddset(&set, SIGTERM);
> +		sigwait(&set, &sig);
> +		exit(0);
> +	}
> +
> +	return pid;
> +}
> +
> +static void join_idle_proc(pid_t pid)
> +{
> +	kill(pid, SIGTERM);
> +	waitpid(pid, NULL, 0);
> +}
> +
> +/*
> + * Test memfd_create() syscall
> + * Verify syscall-argument validation, including name checks, flag validation
> + * and more.
> + */
> +static void test_create(void)
> +{
> +	char buf[2048];
> +	int fd;
> +
> +	/* test NULL name */
> +	mfd_fail_new(NULL, 0, 0);
> +
> +	/* test over-long name (not zero-terminated) */
> +	memset(buf, 0xff, sizeof(buf));
> +	mfd_fail_new(buf, 0, 0);
> +
> +	/* test over-long zero-terminated name */
> +	memset(buf, 0xff, sizeof(buf));
> +	buf[sizeof(buf) - 1] = 0;
> +	mfd_fail_new(buf, 0, 0);
> +
> +	/* verify "" is a valid name */
> +	fd = mfd_assert_new("", 0, 0);
> +	close(fd);
> +
> +	/* verify invalid O_* open flags */
> +	mfd_fail_new("", 0, 0x0100);
> +	mfd_fail_new("", 0, ~MFD_CLOEXEC);
> +	mfd_fail_new("", 0, ~MFD_ALLOW_SEALING);
> +	mfd_fail_new("", 0, ~0);
> +	mfd_fail_new("", 0, 0x8000000000000000ULL);
> +
> +	/* verify MFD_CLOEXEC is allowed */
> +	fd = mfd_assert_new("", 0, MFD_CLOEXEC);
> +	close(fd);
> +
> +	/* verify MFD_ALLOW_SEALING is allowed */
> +	fd = mfd_assert_new("", 0, MFD_ALLOW_SEALING);
> +	close(fd);
> +
> +	/* verify MFD_ALLOW_SEALING | MFD_CLOEXEC is allowed */
> +	fd = mfd_assert_new("", 0, MFD_ALLOW_SEALING | MFD_CLOEXEC);
> +	close(fd);
> +}
> +
> +/*
> + * Test basic sealing
> + * A very basic sealing test to see whether setting/retrieving seals works.
> + */
> +static void test_basic(void)
> +{
> +	int fd;
> +
> +	fd = mfd_assert_new("kern_memfd_basic",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +
> +	/* add basic seals */
> +	mfd_assert_has_seals(fd, 0);
> +	mfd_assert_add_seals(fd, F_SEAL_SHRINK |
> +				 F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd, F_SEAL_SHRINK |
> +				 F_SEAL_WRITE);
> +
> +	/* add them again */
> +	mfd_assert_add_seals(fd, F_SEAL_SHRINK |
> +				 F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd, F_SEAL_SHRINK |
> +				 F_SEAL_WRITE);
> +
> +	/* add more seals and seal against sealing */
> +	mfd_assert_add_seals(fd, F_SEAL_GROW | F_SEAL_SEAL);
> +	mfd_assert_has_seals(fd, F_SEAL_SHRINK |
> +				 F_SEAL_GROW |
> +				 F_SEAL_WRITE |
> +				 F_SEAL_SEAL);
> +
> +	/* verify that sealing no longer works */
> +	mfd_fail_add_seals(fd, F_SEAL_GROW);
> +	mfd_fail_add_seals(fd, 0);
> +
> +	close(fd);
> +
> +	/* verify sealing does not work without MFD_ALLOW_SEALING */
> +	fd = mfd_assert_new("kern_memfd_basic",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC);
> +	mfd_fail_get_seals(fd);
> +	mfd_fail_add_seals(fd, F_SEAL_SHRINK |
> +			       F_SEAL_GROW |
> +			       F_SEAL_WRITE);
> +	mfd_fail_get_seals(fd);
> +	close(fd);
> +}
> +
> +/*
> + * Test SEAL_WRITE
> + * Test whether SEAL_WRITE actually prevents modifications.
> + */
> +static void test_seal_write(void)
> +{
> +	int fd;
> +
> +	fd = mfd_assert_new("kern_memfd_seal_write",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +	mfd_assert_add_seals(fd, F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE);
> +
> +	mfd_assert_read(fd);
> +	mfd_fail_write(fd);
> +	mfd_assert_shrink(fd);
> +	mfd_assert_grow(fd);
> +	mfd_fail_grow_write(fd);
> +
> +	close(fd);
> +}
> +
> +/*
> + * Test SEAL_SHRINK
> + * Test whether SEAL_SHRINK actually prevents shrinking
> + */
> +static void test_seal_shrink(void)
> +{
> +	int fd;
> +
> +	fd = mfd_assert_new("kern_memfd_seal_shrink",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +	mfd_assert_add_seals(fd, F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd, F_SEAL_SHRINK);
> +
> +	mfd_assert_read(fd);
> +	mfd_assert_write(fd);
> +	mfd_fail_shrink(fd);
> +	mfd_assert_grow(fd);
> +	mfd_assert_grow_write(fd);
> +
> +	close(fd);
> +}
> +
> +/*
> + * Test SEAL_GROW
> + * Test whether SEAL_GROW actually prevents growing
> + */
> +static void test_seal_grow(void)
> +{
> +	int fd;
> +
> +	fd = mfd_assert_new("kern_memfd_seal_grow",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +	mfd_assert_add_seals(fd, F_SEAL_GROW);
> +	mfd_assert_has_seals(fd, F_SEAL_GROW);
> +
> +	mfd_assert_read(fd);
> +	mfd_assert_write(fd);
> +	mfd_assert_shrink(fd);
> +	mfd_fail_grow(fd);
> +	mfd_fail_grow_write(fd);
> +
> +	close(fd);
> +}
> +
> +/*
> + * Test SEAL_SHRINK | SEAL_GROW
> + * Test whether SEAL_SHRINK | SEAL_GROW actually prevents resizing
> + */
> +static void test_seal_resize(void)
> +{
> +	int fd;
> +
> +	fd = mfd_assert_new("kern_memfd_seal_resize",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +	mfd_assert_add_seals(fd, F_SEAL_SHRINK | F_SEAL_GROW);
> +	mfd_assert_has_seals(fd, F_SEAL_SHRINK | F_SEAL_GROW);
> +
> +	mfd_assert_read(fd);
> +	mfd_assert_write(fd);
> +	mfd_fail_shrink(fd);
> +	mfd_fail_grow(fd);
> +	mfd_fail_grow_write(fd);
> +
> +	close(fd);
> +}
> +
> +/*
> + * Test sharing via dup()
> + * Test that seals are shared between dupped FDs and they're all equal.
> + */
> +static void test_share_dup(void)
> +{
> +	int fd, fd2;
> +
> +	fd = mfd_assert_new("kern_memfd_share_dup",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +
> +	fd2 = mfd_assert_dup(fd);
> +	mfd_assert_has_seals(fd2, 0);
> +
> +	mfd_assert_add_seals(fd, F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd2, F_SEAL_WRITE);
> +
> +	mfd_assert_add_seals(fd2, F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE | F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd2, F_SEAL_WRITE | F_SEAL_SHRINK);
> +
> +	mfd_assert_add_seals(fd, F_SEAL_SEAL);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_SEAL);
> +	mfd_assert_has_seals(fd2, F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_SEAL);
> +
> +	mfd_fail_add_seals(fd, F_SEAL_GROW);
> +	mfd_fail_add_seals(fd2, F_SEAL_GROW);
> +	mfd_fail_add_seals(fd, F_SEAL_SEAL);
> +	mfd_fail_add_seals(fd2, F_SEAL_SEAL);
> +
> +	close(fd2);
> +
> +	mfd_fail_add_seals(fd, F_SEAL_GROW);
> +	close(fd);
> +}
> +
> +/*
> + * Test sealing with active mmap()s
> + * Modifying seals is only allowed if no other mmap() refs exist.
> + */
> +static void test_share_mmap(void)
> +{
> +	int fd;
> +	void *p;
> +
> +	fd = mfd_assert_new("kern_memfd_share_mmap",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +
> +	/* shared/writable ref prevents sealing */
> +	p = mfd_assert_mmap_shared(fd);
> +	mfd_fail_add_seals(fd, F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd, 0);
> +	munmap(p, MFD_DEF_SIZE);
> +
> +	/* readable ref allows sealing */
> +	p = mfd_assert_mmap_private(fd);
> +	mfd_assert_add_seals(fd, F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd, F_SEAL_SHRINK);
> +	munmap(p, MFD_DEF_SIZE);
> +
> +	close(fd);
> +}
> +
> +/*
> + * Test sealing with open(/proc/self/fd/%d)
> + * Via /proc we can get access to a separate file-context for the same memfd.
> + * This is *not* like dup(), but like a real separate open(). Make sure the
> + * semantics are as expected and we correctly check for RDONLY / WRONLY / RDWR.
> + */
> +static void test_share_open(void)
> +{
> +	int fd, fd2;
> +
> +	fd = mfd_assert_new("kern_memfd_share_open",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +
> +	fd2 = mfd_assert_open(fd, O_RDWR, 0);
> +	mfd_assert_add_seals(fd, F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd2, F_SEAL_WRITE);
> +
> +	mfd_assert_add_seals(fd2, F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE | F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd2, F_SEAL_WRITE | F_SEAL_SHRINK);
> +
> +	close(fd);
> +	fd = mfd_assert_open(fd2, O_RDONLY, 0);
> +
> +	mfd_fail_add_seals(fd, F_SEAL_SEAL);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE | F_SEAL_SHRINK);
> +	mfd_assert_has_seals(fd2, F_SEAL_WRITE | F_SEAL_SHRINK);
> +
> +	close(fd2);
> +	fd2 = mfd_assert_open(fd, O_RDWR, 0);
> +
> +	mfd_assert_add_seals(fd2, F_SEAL_SEAL);
> +	mfd_assert_has_seals(fd, F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_SEAL);
> +	mfd_assert_has_seals(fd2, F_SEAL_WRITE | F_SEAL_SHRINK | F_SEAL_SEAL);
> +
> +	close(fd2);
> +	close(fd);
> +}
> +
> +/*
> + * Test sharing via fork()
> + * Test whether seal-modifications work as expected with forked childs.
> + */
> +static void test_share_fork(void)
> +{
> +	int fd;
> +	pid_t pid;
> +
> +	fd = mfd_assert_new("kern_memfd_share_fork",
> +			    MFD_DEF_SIZE,
> +			    MFD_CLOEXEC | MFD_ALLOW_SEALING);
> +	mfd_assert_has_seals(fd, 0);
> +
> +	pid = spawn_idle_proc();
> +	mfd_assert_add_seals(fd, F_SEAL_SEAL);
> +	mfd_assert_has_seals(fd, F_SEAL_SEAL);
> +
> +	mfd_fail_add_seals(fd, F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd, F_SEAL_SEAL);
> +
> +	join_idle_proc(pid);
> +
> +	mfd_fail_add_seals(fd, F_SEAL_WRITE);
> +	mfd_assert_has_seals(fd, F_SEAL_SEAL);
> +
> +	close(fd);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	pid_t pid;
> +
> +	printf("memfd: CREATE\n");
> +	test_create();
> +	printf("memfd: BASIC\n");
> +	test_basic();
> +
> +	printf("memfd: SEAL-WRITE\n");
> +	test_seal_write();
> +	printf("memfd: SEAL-SHRINK\n");
> +	test_seal_shrink();
> +	printf("memfd: SEAL-GROW\n");
> +	test_seal_grow();
> +	printf("memfd: SEAL-RESIZE\n");
> +	test_seal_resize();
> +
> +	printf("memfd: SHARE-DUP\n");
> +	test_share_dup();
> +	printf("memfd: SHARE-MMAP\n");
> +	test_share_mmap();
> +	printf("memfd: SHARE-OPEN\n");
> +	test_share_open();
> +	printf("memfd: SHARE-FORK\n");
> +	test_share_fork();
> +
> +	/* Run test-suite in a multi-threaded environment with a shared
> +	 * file-table. */
> +	pid = spawn_idle_thread();
> +	printf("memfd: SHARE-DUP (shared file-table)\n");
> +	test_share_dup();
> +	printf("memfd: SHARE-MMAP (shared file-table)\n");
> +	test_share_mmap();
> +	printf("memfd: SHARE-OPEN (shared file-table)\n");
> +	test_share_open();
> +	printf("memfd: SHARE-FORK (shared file-table)\n");
> +	test_share_fork();
> +	join_idle_thread(pid);
> +
> +	printf("memfd: DONE\n");
> +
> +	return 0;
> +}
> -- 
> 1.9.2
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