[FFmpeg-cvslog] avcodec/svq3: perform residual slice copy before xor'ing watermark key

[Peter Ross]

ffmpeg | branch: master | Peter Ross <pross at xvid.org> | Tue Nov  1 10:16:43 2022 +1100| [95386b7b65dab6fb72bf76c14470904782642ebc] | committer: Peter Ross

avcodec/svq3: perform residual slice copy before xor'ing watermark key

Fixes ticket #5387

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=95386b7b65dab6fb72bf76c14470904782642ebc
---

 libavcodec/svq3.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/libavcodec/svq3.c b/libavcodec/svq3.c
index 7e8f16cc72..b96c4f61f6 100644
--- a/libavcodec/svq3.c
+++ b/libavcodec/svq3.c
@@ -1037,15 +1037,16 @@ static int svq3_decode_slice_header(AVCodecContext *avctx)
         }
         memcpy(s->slice_buf, s->gb.buffer + s->gb.index / 8, slice_bytes);
 
+        if (length > 0) {
+            memmove(s->slice_buf, &s->slice_buf[slice_length], length - 1);
+        }
+
         if (s->watermark_key) {
             uint32_t header = AV_RL32(&s->slice_buf[1]);
             AV_WL32(&s->slice_buf[1], header ^ s->watermark_key);
         }
         init_get_bits(&s->gb_slice, s->slice_buf, slice_bits);
 
-        if (length > 0) {
-            memmove(s->slice_buf, &s->slice_buf[slice_length], length - 1);
-        }
         skip_bits_long(&s->gb, slice_bytes * 8);
     }