[PATCH v7 1/1] audio/jack: fix use after free segfault

[Geoffrey McRae]

This change registers a bottom handler to close the JACK client
connection when a server shutdown signal is recieved. Without this
libjack2 attempts to "clean up" old clients and causes a use after free
segfault.

Signed-off-by: Geoffrey McRae <ge...@hostfission.com>
---
 audio/jackaudio.c | 51 +++++++++++++++++++++++++++++++++--------------
 ui/spice-input.c  |  2 ++
 2 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/audio/jackaudio.c b/audio/jackaudio.c
index 72ed7c4929..3492c6b63b 100644
--- a/audio/jackaudio.c
+++ b/audio/jackaudio.c
@@ -25,6 +25,7 @@
 #include "qemu/osdep.h"
 #include "qemu/module.h"
 #include "qemu/atomic.h"
+#include "qemu/main-loop.h"
 #include "qemu-common.h"
 #include "audio.h"
 
@@ -63,6 +64,7 @@ typedef struct QJackClient {
     QJackState      state;
     jack_client_t  *client;
     jack_nframes_t  freq;
+    QEMUBH         *shutdown_bh;
 
     struct QJack   *j;
     int             nchannels;
@@ -306,21 +308,27 @@ static int qjack_xrun(void *arg)
     return 0;
 }
 
+static void qjack_shutdown_bh(void *opaque)
+{
+    QJackClient *c = (QJackClient *)opaque;
+    qjack_client_fini(c);
+}
+
 static void qjack_shutdown(void *arg)
 {
     QJackClient *c = (QJackClient *)arg;
     c->state = QJACK_STATE_SHUTDOWN;
+    qemu_bh_schedule(c->shutdown_bh);
 }
 
 static void qjack_client_recover(QJackClient *c)
 {
-    if (c->state == QJACK_STATE_SHUTDOWN) {
-        qjack_client_fini(c);
+    if (c->state != QJACK_STATE_DISCONNECTED) {
+        return;
     }
 
     /* packets is used simply to throttle this */
-    if (c->state == QJACK_STATE_DISCONNECTED &&
-        c->packets % 100 == 0) {
+    if (c->packets % 100 == 0) {
 
         /* if enabled then attempt to recover */
         if (c->enabled) {
@@ -417,6 +425,7 @@ static int qjack_client_init(QJackClient *c)
         options |= JackServerName;
     }
 
+    c->shutdown_bh = qemu_bh_new(qjack_shutdown_bh, c);
     c->client = jack_client_open(client_name, options, &status,
       c->opt->server_name);
 
@@ -489,8 +498,6 @@ static int qjack_init_out(HWVoiceOut *hw, struct 
audsettings *as,
     QJackOut *jo  = (QJackOut *)hw;
     Audiodev *dev = (Audiodev *)drv_opaque;
 
-    qjack_client_fini(&jo->c);
-
     jo->c.out       = true;
     jo->c.enabled   = false;
     jo->c.nchannels = as->nchannels;
@@ -525,8 +532,6 @@ static int qjack_init_in(HWVoiceIn *hw, struct audsettings 
*as,
     QJackIn  *ji  = (QJackIn *)hw;
     Audiodev *dev = (Audiodev *)drv_opaque;
 
-    qjack_client_fini(&ji->c);
-
     ji->c.out       = false;
     ji->c.enabled   = false;
     ji->c.nchannels = as->nchannels;
@@ -563,29 +568,45 @@ static void qjack_client_fini(QJackClient *c)
         /* fallthrough */
 
     case QJACK_STATE_SHUTDOWN:
+        qemu_bh_delete(c->shutdown_bh);
+        c->shutdown_bh = NULL;
+
         jack_client_close(c->client);
+        c->client = NULL;
+
+        qjack_buffer_free(&c->fifo);
+        g_free(c->port);
+
+        c->state = QJACK_STATE_DISCONNECTED;
         /* fallthrough */
 
     case QJACK_STATE_DISCONNECTED:
         break;
     }
-
-    qjack_buffer_free(&c->fifo);
-    g_free(c->port);
-
-    c->state = QJACK_STATE_DISCONNECTED;
 }
 
 static void qjack_fini_out(HWVoiceOut *hw)
 {
     QJackOut *jo = (QJackOut *)hw;
-    qjack_client_fini(&jo->c);
+
+    qemu_mutex_lock_iothread();
+    if (jo->c.state != QJACK_STATE_DISCONNECTED) {
+        qemu_bh_cancel(jo->c.shutdown_bh);
+        qjack_client_fini(&jo->c);
+    }
+    qemu_mutex_unlock_iothread();
 }
 
 static void qjack_fini_in(HWVoiceIn *hw)
 {
     QJackIn *ji = (QJackIn *)hw;
-    qjack_client_fini(&ji->c);
+
+    qemu_mutex_lock_iothread();
+    if (ji->c.state != QJACK_STATE_DISCONNECTED) {
+        qemu_bh_cancel(ji->c.shutdown_bh);
+        qjack_client_fini(&ji->c);
+    }
+    qemu_mutex_unlock_iothread();
 }
 
 static void qjack_enable_out(HWVoiceOut *hw, bool enable)
-- 
2.20.1