[FFmpeg-cvslog] 4xm: do not overread the source buffer in decode_p_block

[Luca Barbato]

ffmpeg | branch: release/0.10 | Luca Barbato <lu_zero at gentoo.org> | Sun Jun  9 18:27:05 2013 +0200| [0c943d1cdd18d0aea4ebc15f18a1152f7a77e5c9] | committer: Reinhard Tartler

4xm: do not overread the source buffer in decode_p_block

Check for out of picture macroblocks before calling mcdc.

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable at libav.org

(cherry picked from commit 94aefb1932be882fd93f66cf790ceb19ff575c19)

Signed-off-by: Reinhard Tartler <siretart at tauware.de>

Conflicts:
	libavcodec/4xm.c

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0c943d1cdd18d0aea4ebc15f18a1152f7a77e5c9
---

 libavcodec/4xm.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/libavcodec/4xm.c b/libavcodec/4xm.c
index e9f08c3..77d15d5 100644
--- a/libavcodec/4xm.c
+++ b/libavcodec/4xm.c
@@ -343,6 +343,10 @@ static void decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src, int lo
         decode_p_block(f, dst             , src             , log2w, log2h, stride);
         decode_p_block(f, dst + (1<<log2w), src + (1<<log2w), log2w, log2h, stride);
     }else if(code == 3 && f->version<2){
+        if (start > src || src > end) {
+            av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
+            return;
+        }
         mcdc(dst, src, log2w, h, stride, 1, 0);
     }else if(code == 4){
         src += f->mv[bytestream2_get_byte(&f->g)];
@@ -352,6 +356,10 @@ static void decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src, int lo
         }
         mcdc(dst, src, log2w, h, stride, 1, bytestream2_get_le16(&f->g2));
     }else if(code == 5){
+        if (start > src || src > end) {
+            av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
+            return;
+        }
         mcdc(dst, src, log2w, h, stride, 0, bytestream2_get_le16(&f->g2));
     }else if(code == 6){
         if(log2w){