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Merge tag 'kselftest-fix-vfork-2024-05-12' of git://git.kernel.org/pu…
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…b/scm/linux/kernel/git/mic/linux

Pull Kselftest fixes from Mickaël Salaün:
 "Fix Kselftest's vfork() side effects.

  As reported by Kernel Test Robot and Sean Christopherson, some
  tests fail since v6.9-rc1 . This is due to the use of vfork() which
  introduced some side effects. Similarly, while making it more generic,
  a previous commit made some Landlock file system tests flaky, and
  subject to the host's file system mount configuration.

  This fixes all these side effects by replacing vfork() with clone3()
  and CLONE_VFORK, which is cleaner (no arbitrary shared memory) and
  makes the Kselftest framework more robust"

Link: https://lore.kernel.org/oe-lkp/202403291015.1fcfa957-oliver.sang@intel.com
Link: https://lore.kernel.org/r/ZjPelW6-AbtYvslu@google.com
Link: https://lore.kernel.org/r/20240511171445.904356-1-mic@digikod.net

* tag 'kselftest-fix-vfork-2024-05-12' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
  selftests/harness: Handle TEST_F()'s explicit exit codes
  selftests/harness: Fix vfork() side effects
  selftests/harness: Share _metadata between forked processes
  selftests/pidfd: Fix wrong expectation
  selftests/harness: Constify fixture variants
  selftests/landlock: Do not allocate memory in fixture data
  selftests/harness: Fix interleaved scheduling leading to race conditions
  selftests/harness: Fix fixture teardown
  selftests/landlock: Fix FS tests when run on a private mount point
  selftests/pidfd: Fix config for pidfd_setns_test
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Linus Torvalds committed May 12, 2024
2 parents 2842076 + 323feb3 commit af300a3
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Showing 4 changed files with 147 additions and 67 deletions.
127 changes: 94 additions & 33 deletions tools/testing/selftests/kselftest_harness.h
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,8 @@
#include <sys/wait.h>
#include <unistd.h>
#include <setjmp.h>
#include <syscall.h>
#include <linux/sched.h>

#include "kselftest.h"

Expand All @@ -80,6 +82,17 @@
# define TH_LOG_ENABLED 1
#endif

/* Wait for the child process to end but without sharing memory mapping. */
static inline pid_t clone3_vfork(void)
{
struct clone_args args = {
.flags = CLONE_VFORK,
.exit_signal = SIGCHLD,
};

return syscall(__NR_clone3, &args, sizeof(args));
}

/**
* TH_LOG()
*
Expand Down Expand Up @@ -281,6 +294,32 @@
* A bare "return;" statement may be used to return early.
*/
#define FIXTURE_TEARDOWN(fixture_name) \
static const bool fixture_name##_teardown_parent; \
__FIXTURE_TEARDOWN(fixture_name)

/**
* FIXTURE_TEARDOWN_PARENT()
* *_metadata* is included so that EXPECT_*, ASSERT_* etc. work correctly.
*
* @fixture_name: fixture name
*
* .. code-block:: c
*
* FIXTURE_TEARDOWN_PARENT(fixture_name) { implementation }
*
* Same as FIXTURE_TEARDOWN() but run this code in a parent process. This
* enables the test process to drop its privileges without impacting the
* related FIXTURE_TEARDOWN_PARENT() (e.g. to remove files from a directory
* where write access was dropped).
*
* To make it possible for the parent process to use *self*, share (MAP_SHARED)
* the fixture data between all forked processes.
*/
#define FIXTURE_TEARDOWN_PARENT(fixture_name) \
static const bool fixture_name##_teardown_parent = true; \
__FIXTURE_TEARDOWN(fixture_name)

#define __FIXTURE_TEARDOWN(fixture_name) \
void fixture_name##_teardown( \
struct __test_metadata __attribute__((unused)) *_metadata, \
FIXTURE_DATA(fixture_name) __attribute__((unused)) *self, \
Expand Down Expand Up @@ -325,7 +364,7 @@
* variant.
*/
#define FIXTURE_VARIANT_ADD(fixture_name, variant_name) \
extern FIXTURE_VARIANT(fixture_name) \
extern const FIXTURE_VARIANT(fixture_name) \
_##fixture_name##_##variant_name##_variant; \
static struct __fixture_variant_metadata \
_##fixture_name##_##variant_name##_object = \
Expand All @@ -337,7 +376,7 @@
__register_fixture_variant(&_##fixture_name##_fixture_object, \
&_##fixture_name##_##variant_name##_object); \
} \
FIXTURE_VARIANT(fixture_name) \
const FIXTURE_VARIANT(fixture_name) \
_##fixture_name##_##variant_name##_variant =

/**
Expand All @@ -355,10 +394,11 @@
* Very similar to TEST() except that *self* is the setup instance of fixture's
* datatype exposed for use by the implementation.
*
* The @test_name code is run in a separate process sharing the same memory
* (i.e. vfork), which means that the test process can update its privileges
* without impacting the related FIXTURE_TEARDOWN() (e.g. to remove files from
* a directory where write access was dropped).
* The _metadata object is shared (MAP_SHARED) with all the potential forked
* processes, which enables them to use EXCEPT_*() and ASSERT_*().
*
* The *self* object is only shared with the potential forked processes if
* FIXTURE_TEARDOWN_PARENT() is used instead of FIXTURE_TEARDOWN().
*/
#define TEST_F(fixture_name, test_name) \
__TEST_F_IMPL(fixture_name, test_name, -1, TEST_TIMEOUT_DEFAULT)
Expand All @@ -379,53 +419,71 @@
struct __fixture_variant_metadata *variant) \
{ \
/* fixture data is alloced, setup, and torn down per call. */ \
FIXTURE_DATA(fixture_name) self; \
FIXTURE_DATA(fixture_name) self_private, *self = NULL; \
pid_t child = 1; \
int status = 0; \
bool jmp = false; \
memset(&self, 0, sizeof(FIXTURE_DATA(fixture_name))); \
/* Makes sure there is only one teardown, even when child forks again. */ \
bool *teardown = mmap(NULL, sizeof(*teardown), \
PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); \
*teardown = false; \
if (sizeof(*self) > 0) { \
if (fixture_name##_teardown_parent) { \
self = mmap(NULL, sizeof(*self), PROT_READ | PROT_WRITE, \
MAP_SHARED | MAP_ANONYMOUS, -1, 0); \
} else { \
memset(&self_private, 0, sizeof(self_private)); \
self = &self_private; \
} \
} \
if (setjmp(_metadata->env) == 0) { \
/* Use the same _metadata. */ \
child = vfork(); \
/* _metadata and potentially self are shared with all forks. */ \
child = clone3_vfork(); \
if (child == 0) { \
fixture_name##_setup(_metadata, &self, variant->data); \
fixture_name##_setup(_metadata, self, variant->data); \
/* Let setup failure terminate early. */ \
if (_metadata->exit_code) \
_exit(0); \
_metadata->setup_completed = true; \
fixture_name##_##test_name(_metadata, &self, variant->data); \
fixture_name##_##test_name(_metadata, self, variant->data); \
} else if (child < 0 || child != waitpid(child, &status, 0)) { \
ksft_print_msg("ERROR SPAWNING TEST GRANDCHILD\n"); \
_metadata->exit_code = KSFT_FAIL; \
} \
} \
else \
jmp = true; \
if (child == 0) { \
if (_metadata->setup_completed && !_metadata->teardown_parent && !jmp) \
fixture_name##_teardown(_metadata, &self, variant->data); \
if (_metadata->setup_completed && !fixture_name##_teardown_parent && \
__sync_bool_compare_and_swap(teardown, false, true)) \
fixture_name##_teardown(_metadata, self, variant->data); \
_exit(0); \
} \
if (_metadata->setup_completed && _metadata->teardown_parent) \
fixture_name##_teardown(_metadata, &self, variant->data); \
if (!WIFEXITED(status) && WIFSIGNALED(status)) \
if (_metadata->setup_completed && fixture_name##_teardown_parent && \
__sync_bool_compare_and_swap(teardown, false, true)) \
fixture_name##_teardown(_metadata, self, variant->data); \
munmap(teardown, sizeof(*teardown)); \
if (self && fixture_name##_teardown_parent) \
munmap(self, sizeof(*self)); \
if (WIFEXITED(status)) { \
if (WEXITSTATUS(status)) \
_metadata->exit_code = WEXITSTATUS(status); \
} else if (WIFSIGNALED(status)) { \
/* Forward signal to __wait_for_test(). */ \
kill(getpid(), WTERMSIG(status)); \
} \
__test_check_assert(_metadata); \
} \
static struct __test_metadata \
_##fixture_name##_##test_name##_object = { \
.name = #test_name, \
.fn = &wrapper_##fixture_name##_##test_name, \
.fixture = &_##fixture_name##_fixture_object, \
.termsig = signal, \
.timeout = tmout, \
.teardown_parent = false, \
}; \
static struct __test_metadata *_##fixture_name##_##test_name##_object; \
static void __attribute__((constructor)) \
_register_##fixture_name##_##test_name(void) \
{ \
__register_test(&_##fixture_name##_##test_name##_object); \
struct __test_metadata *object = mmap(NULL, sizeof(*object), \
PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); \
object->name = #test_name; \
object->fn = &wrapper_##fixture_name##_##test_name; \
object->fixture = &_##fixture_name##_fixture_object; \
object->termsig = signal; \
object->timeout = tmout; \
_##fixture_name##_##test_name##_object = object; \
__register_test(object); \
} \
static void fixture_name##_##test_name( \
struct __test_metadata __attribute__((unused)) *_metadata, \
Expand Down Expand Up @@ -833,11 +891,12 @@ struct __test_xfail {
{ \
.fixture = &_##fixture_name##_fixture_object, \
.variant = &_##fixture_name##_##variant_name##_object, \
.test = &_##fixture_name##_##test_name##_object, \
}; \
static void __attribute__((constructor)) \
_register_##fixture_name##_##variant_name##_##test_name##_xfail(void) \
{ \
_##fixture_name##_##variant_name##_##test_name##_xfail.test = \
_##fixture_name##_##test_name##_object; \
__register_xfail(&_##fixture_name##_##variant_name##_##test_name##_xfail); \
}

Expand Down Expand Up @@ -880,7 +939,6 @@ struct __test_metadata {
bool timed_out; /* did this test timeout instead of exiting? */
bool aborted; /* stopped test due to failed ASSERT */
bool setup_completed; /* did setup finish? */
bool teardown_parent; /* run teardown in a parent process */
jmp_buf env; /* for exiting out of test early */
struct __test_results *results;
struct __test_metadata *prev, *next;
Expand Down Expand Up @@ -1164,6 +1222,9 @@ void __run_test(struct __fixture_metadata *f,
/* reset test struct */
t->exit_code = KSFT_PASS;
t->trigger = 0;
t->aborted = false;
t->setup_completed = false;
memset(t->env, 0, sizeof(t->env));
memset(t->results->reason, 0, sizeof(t->results->reason));

if (asprintf(&test_name, "%s%s%s.%s", f->name,
Expand All @@ -1179,7 +1240,7 @@ void __run_test(struct __fixture_metadata *f,
fflush(stdout);
fflush(stderr);

t->pid = fork();
t->pid = clone3_vfork();
if (t->pid < 0) {
ksft_print_msg("ERROR SPAWNING TEST CHILD\n");
t->exit_code = KSFT_FAIL;
Expand Down
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