avcodec/vp3: check current_frame before accessing it

Fixes null pointer dereference
Fixes: b15eb06e0111e94bc59123c86db7aff9_signal_sigsegv_a0500f_45_320vp3.nsv with allocation limit  536870912
Found-by: Samuel Groß, Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/vp3.c b/libavcodec/vp3.c
index 005f043b0fc6d91098b77524cd39ba9df273818c..2492026cb6404593f6ecac335e0a78ee8b8e098f 100644 (file)
--- a/libavcodec/vp3.c
+++ b/libavcodec/vp3.c
@@ -1947,6 +1947,8 @@ static int vp3_update_thread_context(AVCodecContext *dst, const AVCodecContext *
     }
 
     if (s != s1) {
+        if (!s->current_frame.f)
+            return AVERROR(ENOMEM);
         // init tables if the first frame hasn't been decoded
         if (!s->current_frame.f->data[0]) {
             int y_fragment_count, c_fragment_count;