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[Launchpad Bug Tracker <1540731@xxxxxxxxxxxxxxxxxx>]

** Branch linked: lp:~ubuntu-branches/ubuntu/trusty/linux-lts-wily
/trusty-proposed

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https://bugs.launchpad.net/bugs/1540731

Title:
  SocketMessenger::update_session_creds() fails to get client PID,
  causing "[ FAILED ]
  PromptSessionClientAPI.client_pid_is_associated_with_session" on
  kernel 4.4 (but kernel 4.3 works)

Status in GLibC:
  New
Status in Mir:
  Invalid
Status in linux package in Ubuntu:
  Fix Released

Bug description:
  Since updating to the 4.4.0-2 kernel recvmsg() fails SCM_CREDENTIALS
  request with EOPNOTSUPP.

  This manifests as a test failure in Mir:

      [ RUN      ] PromptSessionClientAPI.client_pid_is_associated_with_session
      unknown file: Failure

  Test case:

  #include <stdlib.h>
  #include <stdio.h>
  #include <sys/socket.h>
  #include <sys/stat.h>
  #include <assert.h>
  #include <errno.h>
  #include <string.h>

  int main()
  {
      enum { server, client, size };
      int socket_fd[size];
      int const opt = 1;

      assert(socketpair(AF_LOCAL, SOCK_STREAM, 0, socket_fd) == 0);

      char const msg[] = "A random message";
      send(socket_fd[client], msg, sizeof msg, MSG_DONTWAIT | MSG_NOSIGNAL);

      assert(setsockopt(socket_fd[server], SOL_SOCKET, SO_PASSCRED,
  &opt, sizeof(opt)) != -1);

      union {
          struct cmsghdr cmh;
          char control[CMSG_SPACE(sizeof(ucred))];
      } control_un;

      control_un.cmh.cmsg_len = CMSG_LEN(sizeof(ucred));
      control_un.cmh.cmsg_level = SOL_SOCKET;
      control_un.cmh.cmsg_type = SCM_CREDENTIALS;

      msghdr msgh;
      msgh.msg_name = NULL;
      msgh.msg_namelen = 0;
      msgh.msg_iov = NULL;
      msgh.msg_iovlen = 0;
      msgh.msg_control = control_un.control;
      msgh.msg_controllen = sizeof(control_un.control);

      errno = 0;

      if (recvmsg(socket_fd[server], &msgh, MSG_PEEK) == -1)
      {
          printf("Error: %s\n", strerror(errno));
          exit(EXIT_FAILURE);
      }
      else
      {
          printf("Success!\n");
          exit(EXIT_SUCCESS);
      }
  }

  ===
  Kernel-Description: recvmsg() fails SCM_CREDENTIALS request with EOPNOTSUPP.

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