mirror of
https://github.com/hyprwm/wlroots-hyprland.git
synced 2024-12-23 10:29:49 +01:00
906c0766df
This is simply a false sense of security, and is worse than just using setuid. CAP_SYS_ADMIN is an extremely serious capability that is effectively as powerful as root. It also required users to be in the input group, which allows any process to keylog the entire system.
251 lines
4.9 KiB
C
251 lines
4.9 KiB
C
#define _POSIX_C_SOURCE 200809L
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#ifdef __FreeBSD__
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#define __BSD_VISIBLE 1
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#include <linux/input.h>
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#endif
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/socket.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include <wlr/config.h>
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#include <wlr/util/log.h>
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#include <xf86drm.h>
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#ifdef __linux__
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#include <sys/sysmacros.h>
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#include <linux/major.h>
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#endif
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#include "backend/session/direct-ipc.h"
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enum { DRM_MAJOR = 226 };
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static bool have_permissions(void) {
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#ifdef __linux__
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if (geteuid() != 0) {
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wlr_log(WLR_ERROR, "Do not have root privileges; cannot become DRM master");
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return false;
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}
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#endif
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return true;
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}
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static void send_msg(int sock, int fd, void *buf, size_t buf_len) {
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char control[CMSG_SPACE(sizeof(fd))] = {0};
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struct iovec iovec = { .iov_base = buf, .iov_len = buf_len };
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struct msghdr msghdr = {0};
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if (buf) {
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msghdr.msg_iov = &iovec;
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msghdr.msg_iovlen = 1;
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}
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if (fd >= 0) {
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msghdr.msg_control = &control;
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msghdr.msg_controllen = sizeof(control);
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struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr);
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*cmsg = (struct cmsghdr) {
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.cmsg_level = SOL_SOCKET,
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.cmsg_type = SCM_RIGHTS,
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.cmsg_len = CMSG_LEN(sizeof(fd)),
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};
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memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
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}
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ssize_t ret;
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do {
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ret = sendmsg(sock, &msghdr, 0);
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} while (ret < 0 && errno == EINTR);
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}
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static ssize_t recv_msg(int sock, int *fd_out, void *buf, size_t buf_len) {
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char control[CMSG_SPACE(sizeof(*fd_out))] = {0};
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struct iovec iovec = { .iov_base = buf, .iov_len = buf_len };
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struct msghdr msghdr = {0};
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if (buf) {
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msghdr.msg_iov = &iovec;
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msghdr.msg_iovlen = 1;
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}
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if (fd_out) {
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msghdr.msg_control = &control;
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msghdr.msg_controllen = sizeof(control);
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}
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ssize_t ret;
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do {
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ret = recvmsg(sock, &msghdr, MSG_CMSG_CLOEXEC);
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} while (ret < 0 && errno == EINTR);
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if (fd_out) {
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struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msghdr);
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if (cmsg) {
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memcpy(fd_out, CMSG_DATA(cmsg), sizeof(*fd_out));
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} else {
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*fd_out = -1;
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}
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}
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return ret;
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}
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enum msg_type {
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MSG_OPEN,
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MSG_SETMASTER,
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MSG_DROPMASTER,
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MSG_END,
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};
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struct msg {
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enum msg_type type;
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char path[256];
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};
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static void communicate(int sock) {
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struct msg msg;
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int drm_fd = -1;
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bool running = true;
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while (running && recv_msg(sock, &drm_fd, &msg, sizeof(msg)) > 0) {
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switch (msg.type) {
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case MSG_OPEN:
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errno = 0;
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// These are the same flags that logind opens files with
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int fd = open(msg.path, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
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int ret = errno;
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if (fd == -1) {
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goto error;
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}
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#ifndef __FreeBSD__
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struct stat st;
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if (fstat(fd, &st) < 0) {
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ret = errno;
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goto error;
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}
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uint32_t maj = major(st.st_rdev);
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if (maj != INPUT_MAJOR && maj != DRM_MAJOR) {
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ret = ENOTSUP;
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goto error;
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}
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if (maj == DRM_MAJOR && drmSetMaster(fd)) {
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ret = errno;
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}
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#else
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int ev;
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struct drm_version dv = {0};
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if (ioctl(fd, EVIOCGVERSION, &ev) == -1 &&
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ioctl(fd, DRM_IOCTL_VERSION, &dv) == -1) {
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ret = ENOTSUP;
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goto error;
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}
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if (dv.version_major != 0 && drmSetMaster(fd)) {
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ret = errno;
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}
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#endif
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error:
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send_msg(sock, ret ? -1 : fd, &ret, sizeof(ret));
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if (fd >= 0) {
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close(fd);
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}
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break;
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case MSG_SETMASTER:
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drmSetMaster(drm_fd);
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close(drm_fd);
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send_msg(sock, -1, NULL, 0);
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break;
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case MSG_DROPMASTER:
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drmDropMaster(drm_fd);
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close(drm_fd);
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send_msg(sock, -1, NULL, 0);
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break;
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case MSG_END:
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running = false;
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send_msg(sock, -1, NULL, 0);
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break;
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}
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}
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close(sock);
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}
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int direct_ipc_open(int sock, const char *path) {
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struct msg msg = { .type = MSG_OPEN };
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snprintf(msg.path, sizeof(msg.path), "%s", path);
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send_msg(sock, -1, &msg, sizeof(msg));
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int fd, err, ret;
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int retry = 0;
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do {
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ret = recv_msg(sock, &fd, &err, sizeof(err));
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} while (ret == 0 && retry++ < 3);
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return err ? -err : fd;
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}
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void direct_ipc_setmaster(int sock, int fd) {
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struct msg msg = { .type = MSG_SETMASTER };
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send_msg(sock, fd, &msg, sizeof(msg));
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recv_msg(sock, NULL, NULL, 0);
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}
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void direct_ipc_dropmaster(int sock, int fd) {
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struct msg msg = { .type = MSG_DROPMASTER };
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send_msg(sock, fd, &msg, sizeof(msg));
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recv_msg(sock, NULL, NULL, 0);
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}
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void direct_ipc_finish(int sock, pid_t pid) {
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struct msg msg = { .type = MSG_END };
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send_msg(sock, -1, &msg, sizeof(msg));
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recv_msg(sock, NULL, NULL, 0);
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waitpid(pid, NULL, 0);
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}
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int direct_ipc_init(pid_t *pid_out) {
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if (!have_permissions()) {
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return -1;
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}
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int sock[2];
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if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sock) < 0) {
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wlr_log_errno(WLR_ERROR, "Failed to create socket pair");
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return -1;
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}
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pid_t pid = fork();
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if (pid < 0) {
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wlr_log_errno(WLR_ERROR, "Fork failed");
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close(sock[0]);
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close(sock[1]);
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return -1;
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} else if (pid == 0) {
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close(sock[0]);
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communicate(sock[1]);
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_Exit(0);
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}
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close(sock[1]);
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*pid_out = pid;
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return sock[0];
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}
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