On Mon, Dec 31, 2018 at 12:27:13AM +0100, Christian Brauner wrote: > 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 Ok, I have something like this in my tree now that tests for pid recycling. I'm going to send it out tomorrow since I reckon Andrew and others will be off today. But fwiw it sits in https://github.com/brauner/linux/commits/2018-12-02/procfds > > 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
