On Sun, Dec 30, 2018 at 03:02:45PM -0600, Serge Hallyn wrote: > On Sat, Dec 29, 2018 at 11:27:56PM +0100, Christian Brauner wrote: > > As suggested by Andrew Morton in [1] add selftests for the new > > sys_pidfd_send_signal() syscall. > > This tests whether we can send a signal to an existing process and whether > > sending a signal to a process that has already exited fails with ESRCH. > > > > [1]: https://lore.kernel.org/lkml/20181228152012.dbf0508c2508138efc5f2bbe@xxxxxxxxxxxxxxxxxxxx/ > > > > Cc: Arnd Bergmann <arnd@xxxxxxxx> > > Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > > Cc: Serge Hallyn <serge@xxxxxxxxxx> > > Acked-by: Serge Hallyn <serge@xxxxxxxxxx> > > Not saying you need to do this, but it would be neat if you could test > sending to a pid which has been recycled :) Yeah, I thought about it but it's a little weird code. First of all, we can't set /proc/sys/kernel/pid_max to a very low value since this is a system wide setting. So we need to recycle a lot via fork(). Something along the lines of: - unshare pid namespace - fork to create pid 1 in new pid namespace - cycle with fork() until pid > 300 since pids lower than 300 are reserved by the kernel. (That means if we simply use the first fork() after we created pid 1 we would never be able to recycle the pid since we skip over it. :)) - get pidfd to the pid > 300 we just created - wait on the pid > 300 - cycle via fork() until we have reached the same pid > 300 again - send SIGSTOP to that recycled process - test that we cannot send SIGCONT to this SIGSTOPed task via the pidfd we received before - send SIGCONT to the SIGSTOPed recycled pid and exit Christian > > > Cc: Jann Horn <jannh@xxxxxxxxxx> > > Cc: Andy Lutomirsky <luto@xxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Oleg Nesterov <oleg@xxxxxxxxxx> > > Cc: Aleksa Sarai <cyphar@xxxxxxxxxx> > > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > > Cc: Florian Weimer <fweimer@xxxxxxxxxx> > > Signed-off-by: Christian Brauner <christian@xxxxxxxxxx> > > --- > > /* Changelog */ > > v6: > > - patch introduced > > v5..v0: > > - patch not present > > --- > > tools/testing/selftests/Makefile | 1 + > > tools/testing/selftests/pidfd/Makefile | 6 + > > tools/testing/selftests/pidfd/pidfd_test.c | 130 +++++++++++++++++++++ > > 3 files changed, 137 insertions(+) > > create mode 100644 tools/testing/selftests/pidfd/Makefile > > create mode 100644 tools/testing/selftests/pidfd/pidfd_test.c > > > > diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile > > index 24b9934fb269..63b0d8a0ebf7 100644 > > --- a/tools/testing/selftests/Makefile > > +++ b/tools/testing/selftests/Makefile > > @@ -27,6 +27,7 @@ TARGETS += net > > TARGETS += netfilter > > TARGETS += networking/timestamping > > TARGETS += nsfs > > +TARGETS += pidfd > > TARGETS += powerpc > > TARGETS += proc > > TARGETS += pstore > > diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile > > new file mode 100644 > > index 000000000000..deaf8073bc06 > > --- /dev/null > > +++ b/tools/testing/selftests/pidfd/Makefile > > @@ -0,0 +1,6 @@ > > +CFLAGS += -g -I../../../../usr/include/ > > + > > +TEST_GEN_PROGS := pidfd_test > > + > > +include ../lib.mk > > + > > diff --git a/tools/testing/selftests/pidfd/pidfd_test.c b/tools/testing/selftests/pidfd/pidfd_test.c > > new file mode 100644 > > index 000000000000..edcd59979b10 > > --- /dev/null > > +++ b/tools/testing/selftests/pidfd/pidfd_test.c > > @@ -0,0 +1,130 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +#define _GNU_SOURCE > > +#include <errno.h> > > +#include <fcntl.h> > > +#include <linux/types.h> > > +#include <signal.h> > > +#include <stdio.h> > > +#include <stdlib.h> > > +#include <string.h> > > +#include <syscall.h> > > +#include <sys/wait.h> > > +#include <unistd.h> > > + > > +#include "../kselftest.h" > > + > > +static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info, > > + unsigned int flags) > > +{ > > + return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags); > > +} > > + > > +static int signal_received; > > + > > +static void do_exit_success(int sig) > > +{ > > + signal_received = 1; > > +} > > + > > +/* > > + * Straightforward test to see whether pidfd_send_signal() works is to send > > + * a signal to ourselves. > > + */ > > +static int test_pidfd_send_signal_simple_success(void) > > +{ > > + int pidfd, ret; > > + const char *test_name = "pidfd_send_signal send SIGUSR1"; > > + > > + pidfd = open("/proc/self", O_DIRECTORY | O_CLOEXEC); > > + if (pidfd < 0) > > + ksft_exit_fail_msg( > > + "%s test: Failed to open process file descriptor\n", > > + test_name); > > + > > + signal(SIGUSR1, do_exit_success); > > + > > + ret = sys_pidfd_send_signal(pidfd, SIGUSR1, NULL, 0); > > + close(pidfd); > > + if (ret < 0) > > + ksft_exit_fail_msg("%s test: Failed to send signal\n", > > + test_name); > > + > > + if (signal_received != 1) > > + ksft_exit_fail_msg("%s test: Failed to receive signal\n", > > + test_name); > > + > > + signal_received = 0; > > + ksft_test_result_pass("%s test: Sent signal\n", test_name); > > + return 0; > > +} > > + > > +static void wait_for_pid(pid_t pid) > > +{ > > + int status, ret; > > + > > +again: > > + ret = waitpid(pid, &status, 0); > > + if (ret == -1) { > > + if (errno == EINTR) > > + goto again; > > + > > + return; > > + } > > + > > + if (ret != pid) > > + goto again; > > +} > > + > > +static int test_pidfd_send_signal_exited_fail(void) > > +{ > > + int pidfd, ret, saved_errno; > > + char buf[256]; > > + pid_t pid; > > + const char *test_name = "pidfd_send_signal signal exited process"; > > + > > + pid = fork(); > > + if (pid < 0) > > + ksft_exit_fail_msg("%s test: Failed to create new process\n", > > + test_name); > > + > > + if (pid == 0) > > + _exit(EXIT_SUCCESS); > > + > > + snprintf(buf, sizeof(buf), "/proc/%d", pid); > > + > > + pidfd = open(buf, O_DIRECTORY | O_CLOEXEC); > > + > > + wait_for_pid(pid); > > + > > + if (pidfd < 0) > > + ksft_exit_fail_msg( > > + "%s test: Failed to open process file descriptor\n", > > + test_name); > > + > > + ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0); > > + saved_errno = errno; > > + close(pidfd); > > + if (ret == 0) > > + ksft_exit_fail_msg( > > + "%s test: Managed to send signal to process even though it should have failed\n", > > + test_name); > > + > > + if (saved_errno != ESRCH) > > + ksft_exit_fail_msg( > > + "%s test: Expected to receive ESRCH as errno value but received %d instead\n", > > + test_name, saved_errno); > > + > > + ksft_test_result_pass("%s test: Failed to send signal as expected\n", > > + test_name); > > + return 0; > > +} > > + > > +int main(int argc, char **argv) > > +{ > > + ksft_print_header(); > > + > > + test_pidfd_send_signal_simple_success(); > > + test_pidfd_send_signal_exited_fail(); > > + > > + return ksft_exit_pass(); > > +} > > -- > > 2.19.1
