The patch titled
Subject: selftests: improve vm.memfd_noexec sysctl tests
has been added to the -mm mm-unstable branch. Its filename is
selftests-improve-vmmemfd_noexec-sysctl-tests.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-improve-vmmemfd_noexec-sysctl-tests.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Aleksa Sarai <cyphar@xxxxxxxxxx>
Subject: selftests: improve vm.memfd_noexec sysctl tests
Date: Mon, 14 Aug 2023 18:41:01 +1000
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@xxxxxxxxxx
Signed-off-by: Aleksa Sarai <cyphar@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>
Cc: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
Cc: Jeff Xu <jeffxu@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/memfd/memfd_test.c | 339 ++++++++++++++-----
1 file changed, 254 insertions(+), 85 deletions(-)
--- a/tools/testing/selftests/memfd/memfd_test.c~selftests-improve-vmmemfd_noexec-sysctl-tests
+++ a/tools/testing/selftests/memfd/memfd_test.c
@@ -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 ch
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
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
}
}
+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
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
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);
+}
- printf("%s sysctl 1\n", memfd_str);
- sysctl_assert_write("1");
- fd = mfd_assert_new("kern_memfd_sysctl_1",
+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);
- printf("%s child ns\n", memfd_str);
- pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn2);
- join_newpid_thread(pid);
+ 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);
+ fd = mfd_assert_new("kern_memfd_sysctl_1_noexec",
+ mfd_def_size,
+ 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();
+
+ return 0;
+}
+
+/*
+ * Test sysctl
+ * A very basic test to make sure the core sysctl semantics work.
+ */
+static void test_sysctl_simple(void)
+{
+ int pid = spawn_thread(CLONE_NEWPID, sysctl_simple_child, NULL);
+
+ join_thread(pid);
}
-static int newpid_thread_fn2(void *arg)
+static int sysctl_nested(void *arg)
{
- test_sysctl_child2();
+ void (*fn)(void) = arg;
+
+ fn();
return 0;
}
-static pid_t spawn_newpid_thread(unsigned int flags, int (*fn)(void *))
+
+static int sysctl_nested_wait(void *arg)
{
- uint8_t *stack;
- pid_t pid;
+ /* Wait for a SIGCONT. */
+ kill(getpid(), SIGSTOP);
+ return sysctl_nested(arg);
+}
- stack = malloc(STACK_SIZE);
- if (!stack) {
- printf("malloc(STACK_SIZE) failed: %m\n");
- abort();
- }
+static void test_sysctl_sysctl1_failset(void)
+{
+ sysctl_fail_write("0");
+ test_sysctl_sysctl1();
+}
- pid = clone(fn,
- stack + STACK_SIZE,
- SIGCHLD | flags,
- NULL);
- if (pid < 0) {
- printf("clone() failed: %m\n");
- abort();
- }
+static void test_sysctl_sysctl2_failset(void)
+{
+ sysctl_fail_write("1");
+ test_sysctl_sysctl2();
- return pid;
+ sysctl_fail_write("0");
+ test_sysctl_sysctl2();
}
-static void join_newpid_thread(pid_t pid)
+static int sysctl_nested_child(void *arg)
{
- int wstatus;
+ int fd;
+ int pid;
- if (waitpid(pid, &wstatus, 0) < 0) {
- printf("newpid thread: waitpid() failed: %m\n");
- abort();
- }
+ 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);
- if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) != 0) {
- printf("newpid thread: exited with non-zero error code %d\n",
- WEXITSTATUS(wstatus));
- abort();
- }
+ 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();
- if (WIFSIGNALED(wstatus)) {
- printf("newpid thread: killed by signal %d\n",
- WTERMSIG(wstatus));
- abort();
- }
+ 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
- * A very basic sealing test to see whether setting/retrieving seals works.
+ * Test sysctl with nested pid namespaces
+ * Make sure that the sysctl nesting semantics work correctly.
*/
-static void test_sysctl(void)
+static void test_sysctl_nested(void)
{
- int pid = spawn_newpid_thread(CLONE_NEWPID, newpid_thread_fn);
+ int pid = spawn_thread(CLONE_NEWPID, sysctl_nested_child, NULL);
- join_newpid_thread(pid);
+ 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;
_
Patches currently in -mm which might be from cyphar@xxxxxxxxxx are
selftests-memfd-error-out-test-process-when-child-test-fails.patch
memfd-do-not-eacces-old-memfd_create-users-with-vmmemfd_noexec=2.patch
memfd-improve-userspace-warnings-for-missing-exec-related-flags.patch
memfd-replace-ratcheting-feature-from-vmmemfd_noexec-with-hierarchy.patch
selftests-improve-vmmemfd_noexec-sysctl-tests.patch
