[vlc-devel] [PATCH 1/4] lib: media_player: release old media earlier

[Hugo Beauzée-Luyssen]

On Fri, Sep 18, 2020, at 9:42 AM, Thomas Guillem wrote:
> md or mp->p_md is not used after. No rick of race since mp->p_md is
Risk*

> always written with the player lock held.
> 
> This fixes a potential null-dereference if the media was already set to
> null and release by the user via libvlc_media_player_set_media().

Given than libvlc_media_release is checking for NULL media, I don't understand the potential null-deref 

> ---
>  lib/media_player.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/media_player.c b/lib/media_player.c
> index 4db7f96af05..26cf6469589 100644
> --- a/lib/media_player.c
> +++ b/lib/media_player.c
> @@ -72,7 +72,10 @@ on_current_media_changed(vlc_player_t *player, 
> input_item_t *new_media,
>          return;
>  
>      if (md)
> +    {
>          media_detach_preparsed_event(md);
> +        libvlc_media_release(md);
> +    }
>  
>      if (new_media)
>      {
> @@ -87,8 +90,6 @@ on_current_media_changed(vlc_player_t *player, 
> input_item_t *new_media,
>      else
>          mp->p_md = NULL;
>  
> -    libvlc_media_release(md);
> -
>      libvlc_event_t event;
>      event.type = libvlc_MediaPlayerMediaChanged;
>      event.u.media_player_media_changed.new_media = mp->p_md;
> -- 
> 2.28.0
> 
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-- 
  Hugo Beauzée-Luyssen
  hugo at beauzee.fr