[PATCH v2 5/5] 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().

Signed-off-by: Aleksa Sarai cyphar@cyphar.com --- tools/testing/selftests/memfd/memfd_test.c | 339 +++++++++++++++++++++-------- 1 file changed, 254 insertions(+), 85 deletions(-)

diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c index 8b7390ad81d1..3df008677239 100644 --- a/tools/testing/selftests/memfd/memfd_test.c +++ b/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 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); +}

- 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(); + + 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");

- if (WIFSIGNALED(wstatus)) { - printf("newpid thread: killed by signal %d\n", - WTERMSIG(wstatus)); - abort(); - } + 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;