[FFmpeg-cvslog] smacker: limit recursion depth of smacker_decode_bigtree

[Andreas Cadhalpun]

ffmpeg | branch: release/2.8 | Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com> | Sat Nov 19 14:21:11 2016 +0100| [8a7b2fbf6f4d902b7ac245ceae7ee1ced5ff9545] | committer: Andreas Cadhalpun

smacker: limit recursion depth of smacker_decode_bigtree

This fixes segmentation faults due to stack-overflow caused by too deep
recursion.

Reviewed-by: Michael Niedermayer <michael at niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
(cherry picked from commit 946ecd19ea752399bccc751c9339ff74b815587e)
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=8a7b2fbf6f4d902b7ac245ceae7ee1ced5ff9545
---

 libavcodec/smacker.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c
index 4014e8d..8dc474c 100644
--- a/libavcodec/smacker.c
+++ b/libavcodec/smacker.c
@@ -131,8 +131,12 @@ static int smacker_decode_tree(GetBitContext *gb, HuffContext *hc, uint32_t pref
 /**
  * Decode header tree
  */
-static int smacker_decode_bigtree(GetBitContext *gb, HuffContext *hc, DBCtx *ctx)
+static int smacker_decode_bigtree(GetBitContext *gb, HuffContext *hc, DBCtx *ctx, int length)
 {
+    if(length > 500) { // Larger length can cause segmentation faults due to too deep recursion.
+        av_log(NULL, AV_LOG_ERROR, "length too long\n");
+        return AVERROR_INVALIDDATA;
+    }
     if (hc->current + 1 >= hc->length) {
         av_log(NULL, AV_LOG_ERROR, "Tree size exceeded!\n");
         return AVERROR_INVALIDDATA;
@@ -161,12 +165,12 @@ static int smacker_decode_bigtree(GetBitContext *gb, HuffContext *hc, DBCtx *ctx
         int r = 0, r_new, t;
 
         t = hc->current++;
-        r = smacker_decode_bigtree(gb, hc, ctx);
+        r = smacker_decode_bigtree(gb, hc, ctx, length + 1);
         if(r < 0)
             return r;
         hc->values[t] = SMK_NODE | r;
         r++;
-        r_new = smacker_decode_bigtree(gb, hc, ctx);
+        r_new = smacker_decode_bigtree(gb, hc, ctx, length + 1);
         if (r_new < 0)
             return r_new;
         return r + r_new;
@@ -277,7 +281,7 @@ static int smacker_decode_header_tree(SmackVContext *smk, GetBitContext *gb, int
         goto error;
     }
 
-    if (smacker_decode_bigtree(gb, &huff, &ctx) < 0)
+    if (smacker_decode_bigtree(gb, &huff, &ctx, 0) < 0)
         err = -1;
     skip_bits1(gb);
     if(ctx.last[0] == -1) ctx.last[0] = huff.current++;