From: Gerd Hoffmann <kraxel@redhat.com>

Date: Fri, 28 Apr 2017 10:42:37 +0200

Subject: [PATCH] input: limit kbd queue depth

Apply a limit to the number of items we accept into the keyboard queue.

Impact: Without this limit vnc clients can exhaust host memory by

sending keyboard events faster than qemu feeds them to the guest.

Fixes: CVE-2017-8379

Cc: P J P <ppandit@redhat.com>

Cc: Huawei PSIRT <PSIRT@huawei.com>

Reported-by: jiangxin1@huawei.com

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

Message-id: 20170428084237.23960-1-kraxel@redhat.com

(cherry picked from commit fa18f36a461984eae50ab957e47ec78dae3c14fc)

---

 ui/input.c | 14 +++++++++++---

 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/ui/input.c b/ui/input.c

index ed88cda6d6..fb1f404095 100644

--- a/ui/input.c

+++ b/ui/input.c

@@ -41,6 +41,8 @@ static QTAILQ_HEAD(QemuInputEventQueueHead, QemuInputEventQueue) kbd_queue =

     QTAILQ_HEAD_INITIALIZER(kbd_queue);

 static QEMUTimer *kbd_timer;

 static uint32_t kbd_default_delay_ms = 10;

+static uint32_t queue_count;

+static uint32_t queue_limit = 1024;

 QemuInputHandlerState *qemu_input_handler_register(DeviceState *dev,

                                                    QemuInputHandler *handler)

@@ -268,6 +270,7 @@ static void qemu_input_queue_process(void *opaque)

             break;

         }

         QTAILQ_REMOVE(queue, item, node);

+        queue_count--;

         g_free(item);

     }

 }

@@ -282,6 +285,7 @@ static void qemu_input_queue_delay(struct QemuInputEventQueueHead *queue,

     item->delay_ms = delay_ms;

     item->timer = timer;

     QTAILQ_INSERT_TAIL(queue, item, node);

+    queue_count++;

     if (start_timer) {

         timer_mod(item->timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL)

@@ -298,6 +302,7 @@ static void qemu_input_queue_event(struct QemuInputEventQueueHead *queue,

     item->src = src;

     item->evt = evt;

     QTAILQ_INSERT_TAIL(queue, item, node);

+    queue_count++;

 }

 static void qemu_input_queue_sync(struct QemuInputEventQueueHead *queue)

@@ -306,6 +311,7 @@ static void qemu_input_queue_sync(struct QemuInputEventQueueHead *queue)

     item->type = QEMU_INPUT_QUEUE_SYNC;

     QTAILQ_INSERT_TAIL(queue, item, node);

+    queue_count++;

 }

 void qemu_input_event_send_impl(QemuConsole *src, InputEvent *evt)

@@ -381,7 +387,7 @@ void qemu_input_event_send_key(QemuConsole *src, KeyValue *key, bool down)

         qemu_input_event_send(src, evt);

         qemu_input_event_sync();

         qapi_free_InputEvent(evt);

-    } else {

+    } else if (queue_count < queue_limit) {

         qemu_input_queue_event(&kbd_queue, src, evt);

         qemu_input_queue_sync(&kbd_queue);

     }

@@ -409,8 +415,10 @@ void qemu_input_event_send_key_delay(uint32_t delay_ms)

         kbd_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL, qemu_input_queue_process,

                                  &kbd_queue);

     }

-    qemu_input_queue_delay(&kbd_queue, kbd_timer,

-                           delay_ms ? delay_ms : kbd_default_delay_ms);

+    if (queue_count < queue_limit) {

+        qemu_input_queue_delay(&kbd_queue, kbd_timer,

+                               delay_ms ? delay_ms : kbd_default_delay_ms);

+    }

 }

 InputEvent *qemu_input_event_new_btn(InputButton btn, bool down)