From: Michael Schenk <michael.schenk@albis-elcon.com>
Date: Fri, 25 Nov 2016 08:36:20 +0000 (+0100)
Subject: matroskadec: prevent access of elements after freeing
X-Git-Url: https://git.sesse.net/?a=commitdiff_plain;h=18b94669372d3d4b6c51e347587ea64acef9dbb8;p=ffmpeg

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@googlemail.com>
---

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index f79511e4f1e..d96e861c489 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: