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Subject[PATCH v8 5/5] selftests/memfd: add tests for MFD_NOEXEC_SEAL MFD_EXEC
Date
From: Jeff Xu <jeffxu@google.com>

Tests to verify MFD_NOEXEC, MFD_EXEC and vm.memfd_noexec sysctl.

Signed-off-by: Jeff Xu <jeffxu@google.com>
Co-developed-by: Daniel Verkamp <dverkamp@chromium.org>
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
tools/testing/selftests/memfd/fuse_test.c | 1 +
tools/testing/selftests/memfd/memfd_test.c | 228 ++++++++++++++++++++-
2 files changed, 224 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/memfd/fuse_test.c b/tools/testing/selftests/memfd/fuse_test.c
index be675002f918..93798c8c5d54 100644
--- a/tools/testing/selftests/memfd/fuse_test.c
+++ b/tools/testing/selftests/memfd/fuse_test.c
@@ -22,6 +22,7 @@
#include <linux/falloc.h>
#include <fcntl.h>
#include <linux/memfd.h>
+#include <linux/types.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index f18a15a1f275..ae71f15f790d 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c
@@ -30,6 +30,14 @@

#define F_SEAL_EXEC 0x0020

+#define F_WX_SEALS (F_SEAL_SHRINK | \
+ F_SEAL_GROW | \
+ F_SEAL_WRITE | \
+ F_SEAL_FUTURE_WRITE | \
+ F_SEAL_EXEC)
+
+#define MFD_NOEXEC_SEAL 0x0008U
+
/*
* Default is not to test hugetlbfs
*/
@@ -80,6 +88,37 @@ static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)
return fd;
}

+static void sysctl_assert_write(const char *val)
+{
+ int fd = open("/proc/sys/vm/memfd_noexec", O_WRONLY | O_CLOEXEC);
+
+ if (fd < 0) {
+ printf("open sysctl failed\n");
+ abort();
+ }
+
+ if (write(fd, val, strlen(val)) < 0) {
+ printf("write sysctl failed\n");
+ abort();
+ }
+}
+
+static void sysctl_fail_write(const char *val)
+{
+ int fd = open("/proc/sys/vm/memfd_noexec", O_WRONLY | O_CLOEXEC);
+
+ if (fd < 0) {
+ printf("open sysctl failed\n");
+ abort();
+ }
+
+ if (write(fd, val, strlen(val)) >= 0) {
+ printf("write sysctl %s succeeded, but failure expected\n",
+ val);
+ abort();
+ }
+}
+
static int mfd_assert_reopen_fd(int fd_in)
{
int fd;
@@ -758,6 +797,9 @@ static void test_create(void)
mfd_fail_new("", ~0);
mfd_fail_new("", 0x80000000U);

+ /* verify EXEC and NOEXEC_SEAL can't both be set */
+ mfd_fail_new("", MFD_EXEC | MFD_NOEXEC_SEAL);
+
/* verify MFD_CLOEXEC is allowed */
fd = mfd_assert_new("", 0, MFD_CLOEXEC);
close(fd);
@@ -969,20 +1011,21 @@ static void test_seal_resize(void)

/*
* Test SEAL_EXEC
- * Test that chmod() cannot change x bits after sealing
+ * Test fd is created with exec and allow sealing.
+ * chmod() cannot change x bits after sealing.
*/
-static void test_seal_exec(void)
+static void test_exec_seal(void)
{
int fd;

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

+ printf("%s Apply SEAL_EXEC\n", memfd_str);
fd = mfd_assert_new("kern_memfd_seal_exec",
mfd_def_size,
- MFD_CLOEXEC | MFD_ALLOW_SEALING);
+ MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_EXEC);

mfd_assert_mode(fd, 0777);
-
mfd_assert_chmod(fd, 0644);

mfd_assert_has_seals(fd, 0);
@@ -996,10 +1039,181 @@ static void test_seal_exec(void)
mfd_fail_chmod(fd, 0700);
mfd_fail_chmod(fd, 0100);
mfd_assert_chmod(fd, 0666);
+ mfd_assert_write(fd);
+ close(fd);
+
+ printf("%s Apply ALL_SEALS\n", memfd_str);
+ fd = mfd_assert_new("kern_memfd_seal_exec",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_EXEC);
+
+ mfd_assert_mode(fd, 0777);
+ mfd_assert_chmod(fd, 0700);
+
+ mfd_assert_has_seals(fd, 0);
+ mfd_assert_add_seals(fd, F_SEAL_EXEC);
+ mfd_assert_has_seals(fd, F_WX_SEALS);

+ mfd_fail_chmod(fd, 0711);
+ mfd_fail_chmod(fd, 0600);
+ mfd_fail_write(fd);
+ close(fd);
+}
+
+/*
+ * Test EXEC_NO_SEAL
+ * Test fd is created with exec and not allow sealing.
+ */
+static void test_exec_no_seal(void)
+{
+ int fd;
+
+ printf("%s EXEC_NO_SEAL\n", memfd_str);
+
+ /* Create with EXEC but without ALLOW_SEALING */
+ fd = mfd_assert_new("kern_memfd_exec_no_sealing",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_EXEC);
+ mfd_assert_mode(fd, 0777);
+ mfd_assert_has_seals(fd, F_SEAL_SEAL);
+ mfd_assert_chmod(fd, 0666);
close(fd);
}

+/*
+ * Test memfd_create with MFD_NOEXEC flag
+ */
+static void test_noexec_seal(void)
+{
+ int fd;
+
+ printf("%s NOEXEC_SEAL\n", memfd_str);
+
+ /* Create with NOEXEC and ALLOW_SEALING */
+ fd = mfd_assert_new("kern_memfd_noexec",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_NOEXEC_SEAL);
+ mfd_assert_mode(fd, 0666);
+ mfd_assert_has_seals(fd, F_SEAL_EXEC);
+ mfd_fail_chmod(fd, 0777);
+ close(fd);
+
+ /* Create with NOEXEC but without ALLOW_SEALING */
+ fd = mfd_assert_new("kern_memfd_noexec",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_NOEXEC_SEAL);
+ mfd_assert_mode(fd, 0666);
+ mfd_assert_has_seals(fd, F_SEAL_EXEC);
+ mfd_fail_chmod(fd, 0777);
+ close(fd);
+}
+
+static void test_sysctl_child(void)
+{
+ int fd;
+
+ printf("%s sysctl 0\n", memfd_str);
+ sysctl_assert_write("0");
+ fd = mfd_assert_new("kern_memfd_sysctl_0",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+ mfd_assert_mode(fd, 0777);
+ mfd_assert_has_seals(fd, 0);
+ mfd_assert_chmod(fd, 0644);
+ close(fd);
+
+ printf("%s sysctl 1\n", memfd_str);
+ sysctl_assert_write("1");
+ fd = mfd_assert_new("kern_memfd_sysctl_1",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+ mfd_assert_mode(fd, 0666);
+ mfd_assert_has_seals(fd, F_SEAL_EXEC);
+ mfd_fail_chmod(fd, 0777);
+ sysctl_fail_write("0");
+ close(fd);
+
+ printf("%s sysctl 2\n", memfd_str);
+ sysctl_assert_write("2");
+ mfd_fail_new("kern_memfd_sysctl_2",
+ MFD_CLOEXEC | MFD_ALLOW_SEALING);
+ sysctl_fail_write("0");
+ sysctl_fail_write("1");
+}
+
+static int newpid_thread_fn(void *arg)
+{
+ test_sysctl_child();
+ return 0;
+}
+
+static void test_sysctl_child2(void)
+{
+ int fd;
+
+ sysctl_fail_write("0");
+ fd = mfd_assert_new("kern_memfd_sysctl_1",
+ mfd_def_size,
+ MFD_CLOEXEC | MFD_ALLOW_SEALING);
+
+ mfd_assert_mode(fd, 0666);
+ mfd_assert_has_seals(fd, F_SEAL_EXEC);
+ mfd_fail_chmod(fd, 0777);
+ close(fd);
+}
+
+static int newpid_thread_fn2(void *arg)
+{
+ test_sysctl_child2();
+ return 0;
+}
+static pid_t spawn_newpid_thread(unsigned int flags, int (*fn)(void *))
+{
+ uint8_t *stack;
+ pid_t pid;
+
+ stack = malloc(STACK_SIZE);
+ if (!stack) {
+ printf("malloc(STACK_SIZE) failed: %m\n");
+ abort();
+ }
+
+ pid = clone(fn,
+ stack + STACK_SIZE,
+ SIGCHLD | flags,
+ NULL);
+ if (pid < 0) {
+ printf("clone() failed: %m\n");
+ abort();
+ }
+
+ return pid;
+}
+
+static void join_newpid_thread(pid_t pid)
+{
+ waitpid(pid, NULL, 0);
+}
+
+/*
+ * Test sysctl
+ * A very basic sealing test to see whether setting/retrieving seals works.
+ */
+static void test_sysctl(void)
+{
+ int pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn);
+
+ join_newpid_thread(pid);
+
+ printf("%s child ns\n", memfd_str);
+ sysctl_assert_write("1");
+
+ pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn2);
+ join_newpid_thread(pid);
+}
+
/*
* Test sharing via dup()
* Test that seals are shared between dupped FDs and they're all equal.
@@ -1173,13 +1387,15 @@ int main(int argc, char **argv)

test_create();
test_basic();
+ test_exec_seal();
+ test_exec_no_seal();
+ test_noexec_seal();

test_seal_write();
test_seal_future_write();
test_seal_shrink();
test_seal_grow();
test_seal_resize();
- test_seal_exec();

test_share_dup("SHARE-DUP", "");
test_share_mmap("SHARE-MMAP", "");
@@ -1195,6 +1411,8 @@ int main(int argc, char **argv)
test_share_fork("SHARE-FORK", SHARED_FT_STR);
join_idle_thread(pid);

+ test_sysctl();
+
printf("memfd: DONE\n");

return 0;
--
2.39.0.rc1.256.g54fd8350bd-goog
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