File fix-upstream-CVE-2020-12049_2.patch of Package dbus-1-x11

commit 272d484283883fa9ff95b69d924fff6cd34842f5
Author: Simon McVittie <smcv@collabora.com>
Date:   Thu Apr 16 14:45:11 2020 +0100

    sysdeps-unix: On MSG_CTRUNC, close the fds we did receive
    
    MSG_CTRUNC indicates that we have received fewer fds that we should
    have done because the buffer was too small, but we were treating it
    as though it indicated that we received *no* fds. If we received any,
    we still have to make sure we close them, otherwise they will be leaked.
    
    On the system bus, if an attacker can induce us to leak fds in this
    way, that's a local denial of service via resource exhaustion.
    
    Reported-by: Kevin Backhouse, GitHub Security Lab
    Fixes: dbus#294
    Fixes: CVE-2020-12049
    Fixes: GHSL-2020-057

diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index e8cd5b33..f9dc2a6e 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -435,18 +435,6 @@ _dbus_read_socket_with_unix_fds (DBusSocket        fd,
       struct cmsghdr *cm;
       dbus_bool_t found = FALSE;
 
-      if (m.msg_flags & MSG_CTRUNC)
-        {
-          /* Hmm, apparently the control data was truncated. The bad
-             thing is that we might have completely lost a couple of fds
-             without chance to recover them. Hence let's treat this as a
-             serious error. */
-
-          errno = ENOSPC;
-          _dbus_string_set_length (buffer, start);
-          return -1;
-        }
-
       for (cm = CMSG_FIRSTHDR(&m); cm; cm = CMSG_NXTHDR(&m, cm))
         if (cm->cmsg_level == SOL_SOCKET && cm->cmsg_type == SCM_RIGHTS)
           {
@@ -501,6 +489,26 @@ _dbus_read_socket_with_unix_fds (DBusSocket        fd,
       if (!found)
         *n_fds = 0;
 
+      if (m.msg_flags & MSG_CTRUNC)
+        {
+          unsigned int i;
+
+          /* Hmm, apparently the control data was truncated. The bad
+             thing is that we might have completely lost a couple of fds
+             without chance to recover them. Hence let's treat this as a
+             serious error. */
+
+          /* We still need to close whatever fds we *did* receive,
+           * otherwise they'll never get closed. (CVE-2020-12049) */
+          for (i = 0; i < *n_fds; i++)
+            close (fds[i]);
+
+          *n_fds = 0;
+          errno = ENOSPC;
+          _dbus_string_set_length (buffer, start);
+          return -1;
+        }
+
       /* put length back (doesn't actually realloc) */
       _dbus_string_set_length (buffer, start + bytes_read);