[FFmpeg-cvslog] avcodec/c93: Check for block overlap.

[Michael Niedermayer]

ffmpeg | branch: release/1.2 | Michael Niedermayer <michaelni at gmx.at> | Tue Apr 16 16:41:21 2013 +0200| [8ded3738d15c9fb83906a5c1a5a04925130edc1f] | committer: Michael Niedermayer

avcodec/c93: Check for block overlap.

Fixes overlapping memcpy()

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
(cherry picked from commit 6b657ac7889738b9ab38924cca4e7c418f6fbc38)

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=8ded3738d15c9fb83906a5c1a5a04925130edc1f
---

 libavcodec/c93.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libavcodec/c93.c b/libavcodec/c93.c
index e5f371b..c6358d5 100644
--- a/libavcodec/c93.c
+++ b/libavcodec/c93.c
@@ -175,7 +175,13 @@ static int decode_frame(AVCodecContext *avctx, void *data,
             case C93_4X4_FROM_PREV:
                 for (j = 0; j < 8; j += 4) {
                     for (i = 0; i < 8; i += 4) {
-                        offset = bytestream2_get_le16(&gb);
+                        int offset = bytestream2_get_le16(&gb);
+                        int from_x = offset % WIDTH;
+                        int from_y = offset / WIDTH;
+                        if (block_type == C93_4X4_FROM_CURR && from_y == y+j &&
+                            (FFABS(from_x - x-i) < 4 || FFABS(from_x - x-i) > WIDTH-4)) {
+                            return AVERROR_INVALIDDATA;
+                        }
                         if ((ret = copy_block(avctx, &out[j*stride+i],
                                               copy_from, offset, 4, stride)) < 0)
                             return ret;