selftests: improve vm.memfd_noexec sysctl tests

This adds proper tests for the nesting functionality of vm.memfd_noexec as
well as some minor cleanups to spawn_*_thread().

Link: https://lkml.kernel.org/r/20230814-memfd-vm-noexec-uapi-fixes-v2-5-7ff9e3e10ba6@cyphar.com
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Daniel Verkamp <dverkamp@chromium.org>
Cc: Dominique Martinet <asmadeus@codewreck.org>
Cc: Jeff Xu <jeffxu@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Aleksa Sarai 2023-08-14 18:41:01 +10:00 committed by Andrew Morton
parent 9876cfe8ec
commit 6469b66e3f

View File

@ -18,6 +18,7 @@
#include <sys/syscall.h>
#include <sys/wait.h>
#include <unistd.h>
#include <ctype.h>
#include "common.h"
@ -43,7 +44,6 @@
*/
static size_t mfd_def_size = MFD_DEF_SIZE;
static const char *memfd_str = MEMFD_STR;
static pid_t spawn_newpid_thread(unsigned int flags, int (*fn)(void *));
static int newpid_thread_fn2(void *arg);
static void join_newpid_thread(pid_t pid);
@ -96,12 +96,12 @@ 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");
printf("open sysctl failed: %m\n");
abort();
}
if (write(fd, val, strlen(val)) < 0) {
printf("write sysctl failed\n");
printf("write sysctl %s failed: %m\n", val);
abort();
}
}
@ -111,7 +111,7 @@ 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");
printf("open sysctl failed: %m\n");
abort();
}
@ -122,6 +122,33 @@ static void sysctl_fail_write(const char *val)
}
}
static void sysctl_assert_equal(const char *val)
{
char *p, buf[128] = {};
int fd = open("/proc/sys/vm/memfd_noexec", O_RDONLY | O_CLOEXEC);
if (fd < 0) {
printf("open sysctl failed: %m\n");
abort();
}
if (read(fd, buf, sizeof(buf)) < 0) {
printf("read sysctl failed: %m\n");
abort();
}
/* Strip trailing whitespace. */
p = buf;
while (!isspace(*p))
p++;
*p = '\0';
if (strcmp(buf, val) != 0) {
printf("unexpected sysctl value: expected %s, got %s\n", val, buf);
abort();
}
}
static int mfd_assert_reopen_fd(int fd_in)
{
int fd;
@ -736,7 +763,7 @@ static int idle_thread_fn(void *arg)
return 0;
}
static pid_t spawn_idle_thread(unsigned int flags)
static pid_t spawn_thread(unsigned int flags, int (*fn)(void *), void *arg)
{
uint8_t *stack;
pid_t pid;
@ -747,10 +774,7 @@ static pid_t spawn_idle_thread(unsigned int flags)
abort();
}
pid = clone(idle_thread_fn,
stack + STACK_SIZE,
SIGCHLD | flags,
NULL);
pid = clone(fn, stack + STACK_SIZE, SIGCHLD | flags, arg);
if (pid < 0) {
printf("clone() failed: %m\n");
abort();
@ -759,6 +783,33 @@ static pid_t spawn_idle_thread(unsigned int flags)
return pid;
}
static void join_thread(pid_t pid)
{
int wstatus;
if (waitpid(pid, &wstatus, 0) < 0) {
printf("newpid thread: waitpid() failed: %m\n");
abort();
}
if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) != 0) {
printf("newpid thread: exited with non-zero error code %d\n",
WEXITSTATUS(wstatus));
abort();
}
if (WIFSIGNALED(wstatus)) {
printf("newpid thread: killed by signal %d\n",
WTERMSIG(wstatus));
abort();
}
}
static pid_t spawn_idle_thread(unsigned int flags)
{
return spawn_thread(flags, idle_thread_fn, NULL);
}
static void join_idle_thread(pid_t pid)
{
kill(pid, SIGTERM);
@ -1111,42 +1162,69 @@ static void test_noexec_seal(void)
close(fd);
}
static void test_sysctl_child(void)
static void test_sysctl_sysctl0(void)
{
int fd;
int pid;
printf("%s sysctl 0\n", memfd_str);
sysctl_assert_write("0");
fd = mfd_assert_new("kern_memfd_sysctl_0",
sysctl_assert_equal("0");
fd = mfd_assert_new("kern_memfd_sysctl_0_dfl",
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);
}
static void test_sysctl_set_sysctl0(void)
{
sysctl_assert_write("0");
test_sysctl_sysctl0();
}
static void test_sysctl_sysctl1(void)
{
int fd;
sysctl_assert_equal("1");
fd = mfd_assert_new("kern_memfd_sysctl_1_dfl",
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);
fd = mfd_assert_new("kern_memfd_sysctl_1_exec",
mfd_def_size,
MFD_CLOEXEC | MFD_EXEC | 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",
fd = mfd_assert_new("kern_memfd_sysctl_1_noexec",
mfd_def_size,
MFD_CLOEXEC | MFD_ALLOW_SEALING);
printf("%s child ns\n", memfd_str);
pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn2);
join_newpid_thread(pid);
MFD_CLOEXEC | MFD_NOEXEC_SEAL | 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_exec",
MFD_EXEC | MFD_CLOEXEC | MFD_ALLOW_SEALING);
static void test_sysctl_set_sysctl1(void)
{
sysctl_assert_write("1");
test_sysctl_sysctl1();
}
static void test_sysctl_sysctl2(void)
{
int fd;
sysctl_assert_equal("2");
fd = mfd_assert_new("kern_memfd_sysctl_2_dfl",
mfd_def_size,
@ -1156,98 +1234,188 @@ static void test_sysctl_child(void)
mfd_fail_chmod(fd, 0777);
close(fd);
fd = mfd_assert_new("kern_memfd_sysctl_2_noexec_seal",
mfd_fail_new("kern_memfd_sysctl_2_exec",
MFD_CLOEXEC | MFD_EXEC | MFD_ALLOW_SEALING);
fd = mfd_assert_new("kern_memfd_sysctl_2_noexec",
mfd_def_size,
MFD_NOEXEC_SEAL | MFD_CLOEXEC | MFD_ALLOW_SEALING);
MFD_CLOEXEC | MFD_NOEXEC_SEAL | MFD_ALLOW_SEALING);
mfd_assert_mode(fd, 0666);
mfd_assert_has_seals(fd, F_SEAL_EXEC);
mfd_fail_chmod(fd, 0777);
close(fd);
sysctl_fail_write("0");
sysctl_fail_write("1");
}
static int newpid_thread_fn(void *arg)
static void test_sysctl_set_sysctl2(void)
{
test_sysctl_child();
return 0;
sysctl_assert_write("2");
test_sysctl_sysctl2();
}
static void test_sysctl_child2(void)
static int sysctl_simple_child(void *arg)
{
int fd;
int pid;
sysctl_fail_write("0");
fd = mfd_assert_new("kern_memfd_sysctl_1",
mfd_def_size,
MFD_CLOEXEC | MFD_ALLOW_SEALING);
printf("%s sysctl 0\n", memfd_str);
test_sysctl_set_sysctl0();
mfd_assert_mode(fd, 0666);
mfd_assert_has_seals(fd, F_SEAL_EXEC);
mfd_fail_chmod(fd, 0777);
close(fd);
}
printf("%s sysctl 1\n", memfd_str);
test_sysctl_set_sysctl1();
printf("%s sysctl 0\n", memfd_str);
test_sysctl_set_sysctl0();
printf("%s sysctl 2\n", memfd_str);
test_sysctl_set_sysctl2();
printf("%s sysctl 1\n", memfd_str);
test_sysctl_set_sysctl1();
printf("%s sysctl 0\n", memfd_str);
test_sysctl_set_sysctl0();
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)
{
int wstatus;
if (waitpid(pid, &wstatus, 0) < 0) {
printf("newpid thread: waitpid() failed: %m\n");
abort();
}
if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) != 0) {
printf("newpid thread: exited with non-zero error code %d\n",
WEXITSTATUS(wstatus));
abort();
}
if (WIFSIGNALED(wstatus)) {
printf("newpid thread: killed by signal %d\n",
WTERMSIG(wstatus));
abort();
}
}
/*
* Test sysctl
* A very basic sealing test to see whether setting/retrieving seals works.
* A very basic test to make sure the core sysctl semantics work.
*/
static void test_sysctl(void)
static void test_sysctl_simple(void)
{
int pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn);
int pid = spawn_thread(CLONE_NEWPID, sysctl_simple_child, NULL);
join_newpid_thread(pid);
join_thread(pid);
}
static int sysctl_nested(void *arg)
{
void (*fn)(void) = arg;
fn();
return 0;
}
static int sysctl_nested_wait(void *arg)
{
/* Wait for a SIGCONT. */
kill(getpid(), SIGSTOP);
return sysctl_nested(arg);
}
static void test_sysctl_sysctl1_failset(void)
{
sysctl_fail_write("0");
test_sysctl_sysctl1();
}
static void test_sysctl_sysctl2_failset(void)
{
sysctl_fail_write("1");
test_sysctl_sysctl2();
sysctl_fail_write("0");
test_sysctl_sysctl2();
}
static int sysctl_nested_child(void *arg)
{
int fd;
int pid;
printf("%s nested sysctl 0\n", memfd_str);
sysctl_assert_write("0");
/* A further nested pidns works the same. */
pid = spawn_thread(CLONE_NEWPID, sysctl_simple_child, NULL);
join_thread(pid);
printf("%s nested sysctl 1\n", memfd_str);
sysctl_assert_write("1");
/* Child inherits our setting. */
pid = spawn_thread(CLONE_NEWPID, sysctl_nested, test_sysctl_sysctl1);
join_thread(pid);
/* Child cannot raise the setting. */
pid = spawn_thread(CLONE_NEWPID, sysctl_nested,
test_sysctl_sysctl1_failset);
join_thread(pid);
/* Child can lower the setting. */
pid = spawn_thread(CLONE_NEWPID, sysctl_nested,
test_sysctl_set_sysctl2);
join_thread(pid);
/* Child lowering the setting has no effect on our setting. */
test_sysctl_sysctl1();
printf("%s nested sysctl 2\n", memfd_str);
sysctl_assert_write("2");
/* Child inherits our setting. */
pid = spawn_thread(CLONE_NEWPID, sysctl_nested, test_sysctl_sysctl2);
join_thread(pid);
/* Child cannot raise the setting. */
pid = spawn_thread(CLONE_NEWPID, sysctl_nested,
test_sysctl_sysctl2_failset);
join_thread(pid);
/* Verify that the rules are actually inherited after fork. */
printf("%s nested sysctl 0 -> 1 after fork\n", memfd_str);
sysctl_assert_write("0");
pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
test_sysctl_sysctl1_failset);
sysctl_assert_write("1");
kill(pid, SIGCONT);
join_thread(pid);
printf("%s nested sysctl 0 -> 2 after fork\n", memfd_str);
sysctl_assert_write("0");
pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
test_sysctl_sysctl2_failset);
sysctl_assert_write("2");
kill(pid, SIGCONT);
join_thread(pid);
/*
* Verify that the current effective setting is saved on fork, meaning
* that the parent lowering the sysctl doesn't affect already-forked
* children.
*/
printf("%s nested sysctl 2 -> 1 after fork\n", memfd_str);
sysctl_assert_write("2");
pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
test_sysctl_sysctl2);
sysctl_assert_write("1");
kill(pid, SIGCONT);
join_thread(pid);
printf("%s nested sysctl 2 -> 0 after fork\n", memfd_str);
sysctl_assert_write("2");
pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
test_sysctl_sysctl2);
sysctl_assert_write("0");
kill(pid, SIGCONT);
join_thread(pid);
printf("%s nested sysctl 1 -> 0 after fork\n", memfd_str);
sysctl_assert_write("1");
pid = spawn_thread(CLONE_NEWPID, sysctl_nested_wait,
test_sysctl_sysctl1);
sysctl_assert_write("0");
kill(pid, SIGCONT);
join_thread(pid);
return 0;
}
/*
* Test sysctl with nested pid namespaces
* Make sure that the sysctl nesting semantics work correctly.
*/
static void test_sysctl_nested(void)
{
int pid = spawn_thread(CLONE_NEWPID, sysctl_nested_child, NULL);
join_thread(pid);
}
/*
@ -1433,6 +1601,9 @@ int main(int argc, char **argv)
test_seal_grow();
test_seal_resize();
test_sysctl_simple();
test_sysctl_nested();
test_share_dup("SHARE-DUP", "");
test_share_mmap("SHARE-MMAP", "");
test_share_open("SHARE-OPEN", "");
@ -1447,8 +1618,6 @@ 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;