sd-bus: when connecting to a kdbus container bus pass error up

poettering · poettering · commit 80b0d3e3116f · 2015-09-01T20:40:24.000+02:00
We rely on the correct error used when opening the kdbus device node,
hence let's make sure we pass it up from the namespaced child process to
the process which actually wants to connect.
diff --git a/src/libsystemd/sd-bus/bus-container.c b/src/libsystemd/sd-bus/bus-container.c
@@ -125,15 +125,22 @@ int bus_container_connect_kernel(sd_bus *b) {
                 struct cmsghdr cmsghdr;
                 uint8_t buf[CMSG_SPACE(sizeof(int))];
         } control = {};
+        int error_buf = 0;
+        struct iovec iov = {
+                .iov_base = &error_buf,
+                .iov_len = sizeof(error_buf),
+        };
         struct msghdr mh = {
                 .msg_control = &control,
                 .msg_controllen = sizeof(control),
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
         };
         struct cmsghdr *cmsg;
         pid_t child;
         siginfo_t si;
-        int r;
-        _cleanup_close_ int fd = -1;
+        int r, fd = -1;
+        ssize_t n;
 
         assert(b);
         assert(b->input_fd < 0);
@@ -178,10 +185,13 @@ int bus_container_connect_kernel(sd_bus *b) {
                         _exit(EXIT_FAILURE);
 
                 if (grandchild == 0) {
-
                         fd = open(b->kernel, O_RDWR|O_NOCTTY|O_CLOEXEC);
-                        if (fd < 0)
+                        if (fd < 0) {
+                                /* Try to send error up */
+                                error_buf = errno;
+                                (void) write(pair[1], &error_buf, sizeof(error_buf));
                                 _exit(EXIT_FAILURE);
+                        }
 
                         cmsg = CMSG_FIRSTHDR(&mh);
                         cmsg->cmsg_level = SOL_SOCKET;
@@ -213,20 +223,17 @@ int bus_container_connect_kernel(sd_bus *b) {
         if (r < 0)
                 return r;
 
-        if (si.si_code != CLD_EXITED)
-                return -EIO;
-
-        if (si.si_status != EXIT_SUCCESS)
-                return -EIO;
-
-        if (recvmsg(pair[0], &mh, MSG_NOSIGNAL|MSG_CMSG_CLOEXEC) < 0)
+        n = recvmsg(pair[0], &mh, MSG_NOSIGNAL|MSG_CMSG_CLOEXEC);
+        if (n < 0)
                 return -errno;
 
-        CMSG_FOREACH(cmsg, &mh)
+        CMSG_FOREACH(cmsg, &mh) {
                 if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
                         int *fds;
                         unsigned n_fds;
 
+                        assert(fd < 0);
+
                         fds = (int*) CMSG_DATA(cmsg);
                         n_fds = (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
 
@@ -237,9 +244,18 @@ int bus_container_connect_kernel(sd_bus *b) {
 
                         fd = fds[0];
                 }
+        }
+
+        /* If there's an fd passed, we are good. */
+        if (fd >= 0) {
+                b->input_fd = b->output_fd = fd;
+                return bus_kernel_take_fd(b);
+        }
 
-        b->input_fd = b->output_fd = fd;
-        fd = -1;
+        /* If there's an error passed, use it */
+        if (n == sizeof(error_buf) && error_buf > 0)
+                return -error_buf;
 
-        return bus_kernel_take_fd(b);
+        /* Otherwise, we have no clue */
+        return -EIO;
 }
