race condition in new_manager_pad gstrtspsrc.c with freeing a DelayedLink and firing the signal no_more_pads_signal_id - gstrtspsrc.c

[Nicolas Dufresne]

Bugs around rtspsrc can be files at bugs.gnome.org, under product
GStreamer, component gst-plugisn-good. Please make sure to test with
the most recent version of GStreamer in case this bug was already
fixed,

Le jeudi 23 février 2017 à 13:00 -0800, Frank VanZile a écrit :
> race condition in new_manager_pad gstrtspsrc.c with freeing a 
> DelayedLink and firing the signal no_more_pads_signal_id
> 
> DelayedLink sets up two signal handlers
>      no_more_pads_signal_id
>      pad_added_signal_id
> 
> I see two different threads going new_manager_pad at the same
> time.   
> the problem is
> 
> line 2587: gst_element_add_pad (GST_ELEMENT_CAST (src), stream-
> >srcpad); 
> will
>      1) calls gst_parse_found_pad will disconnect the signal
> handlers 
> for no_more_pads_signal_id and pad_added_signal_id
>      2) calls gst_parse_free_delayed_link to free the DelayedLink
> 
> line 2593: gst_element_no_more_pads (GST_ELEMENT_CAST (src));
>      1) will fire the no_more_pads_signal_id single handler for the 
> DelayedLink and calls gst_parse_no_more_pad to log DelayedLink
> information
> 
> So, based on random chance one thread is in gst_element_no_more_pads
> and 
> is processing the signal for no_more_pads_signal_id.
> Then another thread is in gst_element_add_pad, disconnects the
> signal 
> handlers (which the signal is already being processed by the first 
> thread) and then g_slice_free the DelayedLink struct.  But, thread 1
> is 
> processing the signal and calling gst_parse_no_more_pad which is
> them 
> trying to use the DelayedLink struct that thread 2 just
> freed.  Memory 
> Exception.
> 
> 
> Gstreamer Version: 1.10.3
> OS: MAC (OSX)
> Pipeline:  rtspsrc debug=false timeout=0 location=%@ latency=%d 
> ntp-sync=false drop-on-latency=true udp-reconnect=true 
> do-retransmission=false max-rtcp-rtp-time-diff=-1 name=rtsp ! 
> rtph264depay name=x2 ! h264parse name=x3 ! vtdec name=x4 ! 
> autovideosink  name=prim
> 
> _______________________________________________
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