[FFmpeg-cvslog] matroskadec: prevent access of elements after freeing

[Michael Schenk]

ffmpeg | branch: master | Michael Schenk <michael.schenk at albis-elcon.com> | Fri Nov 25 09:36:20 2016 +0100| [18b94669372d3d4b6c51e347587ea64acef9dbb8] | committer: Andreas Cadhalpun

matroskadec: prevent access of elements after freeing

Using the decode interrupt feature of ffmpeg may cause crashes by
accessing previously freed pointers in matroska_read_close.

To prevent this reset nb_elem to zero after freeing the elements,
because ffmpeg normally tests for nb_elem.

Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=18b94669372d3d4b6c51e347587ea64acef9dbb8
---

 libavformat/matroskadec.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index f79511e..d96e861 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -1237,6 +1237,7 @@ static void ebml_free(EbmlSyntax *syntax, void *data)
                      j++, ptr += syntax[i].list_elem_size)
                     ebml_free(syntax[i].def.n, ptr);
                 av_freep(&list->elem);
+                list->nb_elem = 0;
             } else
                 ebml_free(syntax[i].def.n, data_off);
         default: