[vlc-devel] [PATCH] lib: media_player: retain libvlc instance when switching

Rémi Denis-Courmont remi at remlab.net
Wed Jul 8 18:27:38 CEST 2020


Not sure what the code tries to do here, but you can't switch the instance underneath a player since the involved underlying VLC objects are tied to the original instance.

This patch seems as wrong as the current code.

Le 8 juillet 2020 17:24:44 GMT+02:00, Alexandre Janniaux <ajanni at videolabs.io> a écrit :
>The media_player instance retains and releases the libvlc instance it's
>created from. When using a different libvlc instance for media_player
>and media, it's using the libvlc instance from the media_t object,
>leading to the release of the wrong libvlc instance, and thus potential
>use-after-free of one instance and leaks of the other.
>It has been spotted since VLCKit creates a shared libvlc instance and
>then can create a new libvlc instance in case the VLCMediaPlayer is
>created with different options, which means that the VLCMediaPlayer and
>the VLCMedia will be bound to different libvlc instances, triggering
>issue described in first paragraph and crashing.
>Refs videolan/VLCKit#189, videolan/VLCKit#116
> lib/media_player.c | 2 ++
> 1 file changed, 2 insertions(+)
>diff --git a/lib/media_player.c b/lib/media_player.c
>index 9c7a7a76aad..3e8636facea 100644
>--- a/lib/media_player.c
>+++ b/lib/media_player.c
>@@ -914,6 +914,8 @@ void libvlc_media_player_set_media(
> /* The policy here is to ignore that we were created using a different
>      * libvlc_instance, because we don't really care */
>+    libvlc_retain(p_md->p_libvlc_instance);
>+    libvlc_release(p_mi->p_libvlc_instance);
>     p_mi->p_libvlc_instance = p_md->p_libvlc_instance;
>     vlc_player_Unlock(p_mi->player);
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