Fix prepare priority queue comparison function in sd-event

Otherwise a disabled event source can get swapped with an enabled one
and cause a severe sd-event malfunction, breaking the event loop.

Closes: #789796

debian/changelog

@@ -4,6 +4,10 @@ systemd (215-17+deb8u5) UNRELEASED; urgency=medium
     services are properly killed after a given timeout. (Closes: #813702)
   * Don't reset log level to NOTICE if we get quiet on the kernel cmdline.
     (Closes: #828006)
+  * Fix prepare priority queue comparison function in sd-event.
+    Otherwise a disabled event source can get swapped with an enabled one
+    and cause a severe sd-event malfunction, breaking the event loop.
+    (Closes: #789796)
 
  -- Michael Biebl <biebl@debian.org>  Fri, 01 Jul 2016 17:35:05 +0200
 

debian/patches/sd-event-fix-prepare-priority-queue-comparison-function.patch

+From: Krzysztof Kotlenga <k.kotlenga@sims.pl>
+Date: Thu, 24 Sep 2015 00:34:51 +0200
+Subject: sd-event: fix prepare priority queue comparison function
+
+Otherwise a disabled event source can get swapped with an enabled one
+and cause a severe sd-event malfunction.
+
+http://lists.freedesktop.org/archives/systemd-devel/2015-September/034356.html
+
+(cherry-picked from commit 8046c4576a68977a1089d2585866bfab8152661b)
+---
+ src/libsystemd/sd-event/sd-event.c | 12 ++++++------
+ 1 file changed, 6 insertions(+), 6 deletions(-)
+
+diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c
+index ecab8f0..fd17439 100644
+--- a/src/libsystemd/sd-event/sd-event.c
++++ b/src/libsystemd/sd-event/sd-event.c
+@@ -228,6 +228,12 @@ static int prepare_prioq_compare(const void *a, const void *b) {
+         assert(x->prepare);
+         assert(y->prepare);
+ 
++        /* Enabled ones first */
++        if (x->enabled != SD_EVENT_OFF && y->enabled == SD_EVENT_OFF)
++                return -1;
++        if (x->enabled == SD_EVENT_OFF && y->enabled != SD_EVENT_OFF)
++                return 1;
++
+         /* Move most recently prepared ones last, so that we can stop
+          * preparing as soon as we hit one that has already been
+          * prepared in the current iteration */
+@@ -236,12 +242,6 @@ static int prepare_prioq_compare(const void *a, const void *b) {
+         if (x->prepare_iteration > y->prepare_iteration)
+                 return 1;
+ 
+-        /* Enabled ones first */
+-        if (x->enabled != SD_EVENT_OFF && y->enabled == SD_EVENT_OFF)
+-                return -1;
+-        if (x->enabled == SD_EVENT_OFF && y->enabled != SD_EVENT_OFF)
+-                return 1;
+-
+         /* Lower priority values first */
+         if (x->priority < y->priority)
+                 return -1;

debian/patches/series

@@ -160,6 +160,7 @@ make-sure-all-swap-units-are-ordered-before-the-swap-targ.patch
 nspawn-fix-network-interface.patch
 service-use-the-right-timeout-for-stop-processes-we-fork.patch
 core-don-t-reset-log-level-to-NOTICE-if-we-get-quiet-on-t.patch
+sd-event-fix-prepare-priority-queue-comparison-function.patch
 
 ## Debian specific patches:
 Add-back-support-for-Debian-specific-config-files.patch