From 5e039e1b4c0fe25c76faa7ea107db60264edb757 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Reimar=20D=C3=B6ffinger?= <Reimar.Doeffinger@gmx.de>
Date: Wed, 8 Jul 2009 19:39:23 +0000
Subject: [PATCH] Add extra validation checks to ff_vorbis_len2vlc. They should
 not be necessary, but it seems like a reasonable precaution.

Originally committed as revision 19374 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/vorbis.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/vorbis.c b/libavcodec/vorbis.c
index 2148c23665..fd0cafa187 100644
--- a/libavcodec/vorbis.c
+++ b/libavcodec/vorbis.c
@@ -45,6 +45,9 @@ unsigned int ff_vorbis_nth_root(unsigned int x, unsigned int n) {   // x^(1/n)
 
 // Generate vlc codes from vorbis huffman code lengths
 
+// the two bits[p] > 32 checks should be redundant, all calling code should
+// already ensure that, but since it allows overwriting the stack it seems
+// reasonable to check redundantly.
 int ff_vorbis_len2vlc(uint8_t *bits, uint32_t *codes, uint_fast32_t num) {
     uint_fast32_t exit_at_level[33]={404,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
         0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
@@ -63,6 +66,7 @@ int ff_vorbis_len2vlc(uint8_t *bits, uint32_t *codes, uint_fast32_t num) {
     }
 
     codes[p]=0;
+    if (bits[p] > 32) return 1;
     for(i=0;i<bits[p];++i) {
         exit_at_level[i+1]=1<<i;
     }
@@ -79,6 +83,7 @@ int ff_vorbis_len2vlc(uint8_t *bits, uint32_t *codes, uint_fast32_t num) {
     ++p;
 
     for(;p<num;++p) {
+        if (bits[p] > 32) return 1;
         if (bits[p]==0) continue;
         // find corresponding exit(node which the tree can grow further from)
         for(i=bits[p];i>0;--i) {