// SPDX-License-Identifier: GPL-2.0

#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <linux/types.h>
#include <poll.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syscall.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/kcmp.h>

#include "pidfd.h"
#include "kselftest_harness.h"

/*
 * UNKNOWN_FD is an fd number that should never exist in the child, as it is
 * used to check the negative case.
 */
#define UNKNOWN_FD 111
#define UID_NOBODY 65535

static int sys_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1,
                    unsigned long idx2)
{
        return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);
}

static int __child(int sk, int memfd)
{
        int ret;
        char buf;

        /*
         * Ensure we don't leave around a bunch of orphaned children if our
         * tests fail.
         */
        ret = prctl(PR_SET_PDEATHSIG, SIGKILL);
        if (ret) {
                fprintf(stderr, "%s: Child could not set DEATHSIG\n",
                        strerror(errno));
                return -1;
        }

        ret = send(sk, &memfd, sizeof(memfd), 0);
        if (ret != sizeof(memfd)) {
                fprintf(stderr, "%s: Child failed to send fd number\n",
                        strerror(errno));
                return -1;
        }

        /*
         * The fixture setup is completed at this point. The tests will run.
         *
         * This blocking recv enables the parent to message the child.
         * Either we will read 'P' off of the sk, indicating that we need
         * to disable ptrace, or we will read a 0, indicating that the other
         * side has closed the sk. This occurs during fixture teardown time,
         * indicating that the child should exit.
         */
        while ((ret = recv(sk, &buf, sizeof(buf), 0)) > 0) {
                if (buf == 'P') {
                        ret = prctl(PR_SET_DUMPABLE, 0);
                        if (ret < 0) {
                                fprintf(stderr,
                                        "%s: Child failed to disable ptrace\n",
                                        strerror(errno));
                                return -1;
                        }
                } else {
                        fprintf(stderr, "Child received unknown command %c\n",
                                buf);
                        return -1;
                }
                ret = send(sk, &buf, sizeof(buf), 0);
                if (ret != 1) {
                        fprintf(stderr, "%s: Child failed to ack\n",
                                strerror(errno));
                        return -1;
                }
        }
        if (ret < 0) {
                fprintf(stderr, "%s: Child failed to read from socket\n",
                        strerror(errno));
                return -1;
        }

        return 0;
}

static int child(int sk)
{
        int memfd, ret;

        memfd = sys_memfd_create("test", 0);
        if (memfd < 0) {
                fprintf(stderr, "%s: Child could not create memfd\n",
                        strerror(errno));
                ret = -1;
        } else {
                ret = __child(sk, memfd);
                close(memfd);
        }

        close(sk);
        return ret;
}

FIXTURE(child)
{
        /*
         * remote_fd is the number of the FD which we are trying to retrieve
         * from the child.
         */
        int remote_fd;
        /* pid points to the child which we are fetching FDs from */
        pid_t pid;
        /* pidfd is the pidfd of the child */
        int pidfd;
        /*
         * sk is our side of the socketpair used to communicate with the child.
         * When it is closed, the child will exit.
         */
        int sk;
        bool ignore_child_result;
};

FIXTURE_SETUP(child)
{
        int ret, sk_pair[2];

        ASSERT_EQ(0, socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sk_pair)) {
                TH_LOG("%s: failed to create socketpair", strerror(errno));
        }
        self->sk = sk_pair[0];

        self->pid = fork();
        ASSERT_GE(self->pid, 0);

        if (self->pid == 0) {
                close(sk_pair[0]);
                if (child(sk_pair[1]))
                        _exit(EXIT_FAILURE);
                _exit(EXIT_SUCCESS);
        }

        close(sk_pair[1]);

        self->pidfd = sys_pidfd_open(self->pid, 0);
        ASSERT_GE(self->pidfd, 0);

        /*
         * Wait for the child to complete setup. It'll send the remote memfd's
         * number when ready.
         */
        ret = recv(sk_pair[0], &self->remote_fd, sizeof(self->remote_fd), 0);
        ASSERT_EQ(sizeof(self->remote_fd), ret);
}

FIXTURE_TEARDOWN(child)
{
        int ret;

        EXPECT_EQ(0, close(self->pidfd));
        EXPECT_EQ(0, close(self->sk));

        ret = wait_for_pid(self->pid);
        if (!self->ignore_child_result)
                EXPECT_EQ(0, ret);
}

TEST_F(child, disable_ptrace)
{
        int uid, fd;
        char c;

        /*
         * Turn into nobody if we're root, to avoid CAP_SYS_PTRACE
         *
         * The tests should run in their own process, so even this test fails,
         * it shouldn't result in subsequent tests failing.
         */
        uid = getuid();
        if (uid == 0)
                ASSERT_EQ(0, seteuid(UID_NOBODY));

        ASSERT_EQ(1, send(self->sk, "P", 1, 0));
        ASSERT_EQ(1, recv(self->sk, &c, 1, 0));

        fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
        EXPECT_EQ(-1, fd);
        EXPECT_EQ(EPERM, errno);

        if (uid == 0)
                ASSERT_EQ(0, seteuid(0));
}

TEST_F(child, fetch_fd)
{
        int fd, ret;

        fd = sys_pidfd_getfd(self->pidfd, self->remote_fd, 0);
        ASSERT_GE(fd, 0);

        ret = sys_kcmp(getpid(), self->pid, KCMP_FILE, fd, self->remote_fd);
        if (ret < 0 && errno == ENOSYS)
                SKIP(return, "kcmp() syscall not supported");
        EXPECT_EQ(ret, 0);

        ret = fcntl(fd, F_GETFD);
        ASSERT_GE(ret, 0);
        EXPECT_GE(ret & FD_CLOEXEC, 0);

        close(fd);
}

TEST_F(child, test_unknown_fd)
{
        int fd;

        fd = sys_pidfd_getfd(self->pidfd, UNKNOWN_FD, 0);
        EXPECT_EQ(-1, fd) {
                TH_LOG("getfd succeeded while fetching unknown fd");
        };
        EXPECT_EQ(EBADF, errno) {
                TH_LOG("%s: getfd did not get EBADF", strerror(errno));
        }
}

TEST(flags_set)
{
        ASSERT_EQ(-1, sys_pidfd_getfd(0, 0, 1));
        EXPECT_EQ(errno, EINVAL);
}

TEST_F(child, no_strange_EBADF)
{
        struct pollfd fds;

        self->ignore_child_result = true;

        fds.fd = self->pidfd;
        fds.events = POLLIN;

        ASSERT_EQ(kill(self->pid, SIGKILL), 0);
        ASSERT_EQ(poll(&fds, 1, 5000), 1);

        /*
         * It used to be that pidfd_getfd() could race with the exiting thread
         * between exit_files() and release_task(), and get a non-null task
         * with a NULL files struct, and you'd get EBADF, which was slightly
         * confusing.
         */
        errno = 0;
        EXPECT_EQ(sys_pidfd_getfd(self->pidfd, self->remote_fd, 0), -1);
        EXPECT_EQ(errno, ESRCH);
}

#if __NR_pidfd_getfd == -1
int main(void)
{
        fprintf(stderr, "__NR_pidfd_getfd undefined. The pidfd_getfd syscall is unavailable. Test aborting\n");
        return KSFT_SKIP;
}
#else
TEST_HARNESS_MAIN
#endif