gnu: dbus: Fix CVE-2020-12049.

* gnu/packages/patches/dbus-CVE-2020-12049.patch: New file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/glib.scm (dbus/fixed): New variable.
(dbus)[replacement]: New field.

gnu/local.mk

@@ -855,6 +855,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/datefudge-gettimeofday.patch		\
   %D%/packages/patches/dbacl-include-locale.h.patch		\
   %D%/packages/patches/dbus-helper-search-path.patch		\
+  %D%/packages/patches/dbus-CVE-2020-12049.patch		\
   %D%/packages/patches/dbus-c++-gcc-compat.patch		\
   %D%/packages/patches/dbus-c++-threading-mutex.patch		\
   %D%/packages/patches/dconf-meson-0.52.patch			\

gnu/packages/glib.scm

@@ -88,6 +88,7 @@
   (package
     (name "dbus")
     (version "1.12.16")
+    (replacement dbus/fixed)
     (source (origin
               (method url-fetch)
               (uri (string-append
@@ -164,6 +165,15 @@ or through unencrypted TCP/IP suitable for use behind a firewall with
 shared NFS home directories.")
     (license license:gpl2+)))                     ; or Academic Free License 2.1
 
+;; Replacement package to fix CVE-2020-12049.
+(define dbus/fixed
+  (package
+    (inherit dbus)
+    (source (origin
+              (inherit (package-source dbus))
+              (patches (append (search-patches "dbus-CVE-2020-12049.patch")
+                               (origin-patches (package-source dbus))))))))
+
 (define glib
   (package
    (name "glib")

gnu/packages/patches/dbus-CVE-2020-12049.patch

@@ -0,0 +1,58 @@
+Fix CVE-2020-12049:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-12049
+https://lists.freedesktop.org/archives/ftp-release/2020-June/000753.html
+
+Taken from upstream:
+
+https://gitlab.freedesktop.org/dbus/dbus/-/commit/272d484283883fa9ff95b69d924fff6cd34842f5
+
+diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
+--- 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);
+