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

[Geoffrey McRae]

Due to a ridiculous commit in the Jack library, the client may have been
freed already by a secondary audio device recovering its session.

https://github.com/jackaudio/jack2/issues/627

Until there is a proper fix for this we can not risk using the pointer
at all if we have been notified of a shutdown as it may have been freed
by the jack library, as such the close call is commented out to prevent
a use after free segfault.

At this time, this will not cause a memory leak as the recovery routine
will trigger the "cleanup" code in the jack library, however, if this is
ever corrected in the jack library this will need to be revisited.

Signed-off-by: Geoffrey McRae <geoff@hostfission.com>
---
 audio/jackaudio.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/audio/jackaudio.c b/audio/jackaudio.c
index 72ed7c4929..e8faf1bb89 100644
--- a/audio/jackaudio.c
+++ b/audio/jackaudio.c
@@ -563,7 +563,22 @@ static void qjack_client_fini(QJackClient *c)
         /* fallthrough */
 
     case QJACK_STATE_SHUTDOWN:
-        jack_client_close(c->client);
+        /*
+         * Due to a rediculous commit in the Jack library, the client may have
+         * been freed already.
+         *
+         * Until there is a proper fix for this we can not risk using the
+         * pointer at all if we have been notified of a shutdown, as such the
+         * below line is commented out to prevent a use after free segfault.
+         * This will not cause a memory leak as the recovery routine will 
trigger
+         * the "cleanup" code in the jack library.
+         *
+         * 
https://github.com/jackaudio/jack2/commit/171a3c4a0ddd18d2afae56f3af6291c8e96ee3ac
+         */
+
+        //jack_client_close(c->client);
+        c->client = NULL;
+
         /* fallthrough */
 
     case QJACK_STATE_DISCONNECTED:
-- 
2.20.1