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selftests/harness: Fix tests timeout and race condition

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We cannot use CLONE_VFORK because we also need to wait for the timeout
signal.

Restore tests timeout by using the original fork() call in __run_test()
but also in __TEST_F_IMPL().  Also fix a race condition when waiting for
the test child process.

Because test metadata are shared between test processes, only the
parent process must set the test PID (child).  Otherwise, t->pid may be
set to zero, leading to inconsistent error cases:

  #  RUN           layout1.rule_on_mountpoint ...
  # rule_on_mountpoint: Test ended in some other way [127]
  #            OK  layout1.rule_on_mountpoint
  ok 20 layout1.rule_on_mountpoint

As safeguards, initialize the "status" variable with a valid exit code,
and handle unknown test exits as errors.

The use of fork() introduces a new race condition in landlock/fs_test.c
which seems to be specific to hostfs bind mounts, but I haven't found
the root cause and it's difficult to trigger.  I'll try to fix it with
another patch.

Cc: Christian Brauner <brauner@kernel.org>
Cc: Günther Noack <gnoack@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/r/9341d4db-5e21-418c-bf9e-9ae2da7877e1@sirena.org.uk
Fixes: a86f18903db9 ("selftests/harness: Fix interleaved scheduling leading to race conditions")
Fixes: 24cf65a62266 ("selftests/harness: Share _metadata between forked processes")
Link: https://lore.kernel.org/r/20240621180605.834676-1-mic@digikod.net
Tested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This commit is contained in:
Mickaël Salaün 2024-06-21 20:06:05 +02:00
parent f2661062f1
commit 130e428067
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GPG Key ID: E5E3D0E88C82F6D2
1 changed files with 24 additions and 19 deletions
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43
tools/testing/selftests/kselftest_harness.h
View File

@ -66,8 +66,6 @@
#include <sys/wait.h>
#include <unistd.h>
#include <setjmp.h>
#include <syscall.h>
#include <linux/sched.h>
#include "kselftest.h"
@ -82,17 +80,6 @@
# 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()
*
@ -437,7 +424,7 @@ static inline pid_t clone3_vfork(void)
} \
if (setjmp(_metadata->env) == 0) { \
/* _metadata and potentially self are shared with all forks. */ \
child = clone3_vfork(); \
child = fork(); \
if (child == 0) { \
fixture_name##_setup(_metadata, self, variant->data); \
/* Let setup failure terminate early. */ \
@ -1016,7 +1003,14 @@ void __wait_for_test(struct __test_metadata *t)
.sa_flags = SA_SIGINFO,
};
struct sigaction saved_action;
int status;
/*
* Sets status so that WIFEXITED(status) returns true and
* WEXITSTATUS(status) returns KSFT_FAIL. This safe default value
* should never be evaluated because of the waitpid(2) check and
* SIGALRM handling.
*/
int status = KSFT_FAIL << 8;
int child;
if (sigaction(SIGALRM, &action, &saved_action)) {
t->exit_code = KSFT_FAIL;
@ -1028,7 +1022,15 @@ void __wait_for_test(struct __test_metadata *t)
__active_test = t;
t->timed_out = false;
alarm(t->timeout);
waitpid(t->pid, &status, 0);
child = waitpid(t->pid, &status, 0);
if (child == -1 && errno != EINTR) {
t->exit_code = KSFT_FAIL;
fprintf(TH_LOG_STREAM,
"# %s: Failed to wait for PID %d (errno: %d)\n",
t->name, t->pid, errno);
return;
}
alarm(0);
if (sigaction(SIGALRM, &saved_action, NULL)) {
t->exit_code = KSFT_FAIL;
@ -1083,6 +1085,7 @@ void __wait_for_test(struct __test_metadata *t)
WTERMSIG(status));
}
} else {
t->exit_code = KSFT_FAIL;
fprintf(TH_LOG_STREAM,
"# %s: Test ended in some other way [%u]\n",
t->name,
@ -1218,6 +1221,7 @@ void __run_test(struct __fixture_metadata *f,
struct __test_xfail *xfail;
char test_name[1024];
const char *diagnostic;
int child;
/* reset test struct */
t->exit_code = KSFT_PASS;
@ -1236,15 +1240,16 @@ void __run_test(struct __fixture_metadata *f,
fflush(stdout);
fflush(stderr);
t->pid = clone3_vfork();
if (t->pid < 0) {
child = fork();
if (child < 0) {
ksft_print_msg("ERROR SPAWNING TEST CHILD\n");
t->exit_code = KSFT_FAIL;
} else if (t->pid == 0) {
} else if (child == 0) {
setpgrp();
t->fn(t, variant);
_exit(t->exit_code);
} else {
t->pid = child;
__wait_for_test(t);
}
ksft_print_msg(" %4s %s\n",