From d974ad0524942882f489914013d08ab16d147170 Mon Sep 17 00:00:00 2001

From: David Herrmann <dh.herrmann@gmail.com>

Date: Thu, 28 Aug 2014 12:42:03 +0200

Subject: [PATCH] bus: fix use-after-free in slot-release

We must not access slot->floating after we possible dropped the last

reference to it. Fix all callback-invocations to first check

slot->floating and possible disconnect the slot, then release the last

reference.

---

 src/libsystemd/sd-bus/sd-bus.c | 12 +++++++++---

 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c

index a204d67590..8caa404227 100644

--- a/src/libsystemd/sd-bus/sd-bus.c

+++ b/src/libsystemd/sd-bus/sd-bus.c

@@ -2107,7 +2107,7 @@ static int process_timeout(sd_bus *bus) {

         r = c->callback(bus, m, slot->userdata, &error_buffer);

         bus->current_userdata = NULL;

         bus->current_handler = NULL;

-        bus->current_slot = sd_bus_slot_unref(slot);

+        bus->current_slot = NULL;

         bus->current_message = NULL;

         if (slot->floating) {

@@ -2115,6 +2115,8 @@ static int process_timeout(sd_bus *bus) {

                 sd_bus_slot_unref(slot);

         }

+        sd_bus_slot_unref(slot);

+

         return bus_maybe_reply_error(m, r, &error_buffer);

 }

@@ -2203,13 +2205,15 @@ static int process_reply(sd_bus *bus, sd_bus_message *m) {

         r = c->callback(bus, m, slot->userdata, &error_buffer);

         bus->current_userdata = NULL;

         bus->current_handler = NULL;

-        bus->current_slot = sd_bus_slot_unref(slot);

+        bus->current_slot = NULL;

         if (slot->floating) {

                 bus_slot_disconnect(slot);

                 sd_bus_slot_unref(slot);

         }

+        sd_bus_slot_unref(slot);

+

         return bus_maybe_reply_error(m, r, &error_buffer);

 }

@@ -2529,7 +2533,7 @@ static int process_closing(sd_bus *bus, sd_bus_message **ret) {

                 r = c->callback(bus, m, slot->userdata, &error_buffer);

                 bus->current_userdata = NULL;

                 bus->current_handler = NULL;

-                bus->current_slot = sd_bus_slot_unref(slot);

+                bus->current_slot = NULL;

                 bus->current_message = NULL;

                 if (slot->floating) {

@@ -2537,6 +2541,8 @@ static int process_closing(sd_bus *bus, sd_bus_message **ret) {

                         sd_bus_slot_unref(slot);

                 }

+                sd_bus_slot_unref(slot);

+

                 return bus_maybe_reply_error(m, r, &error_buffer);

         }