prores: Reject negative run and level values

Sample-Id: 00000611-google

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

libavcodec/proresdec.c

@@ -393,12 +393,16 @@ static inline int decode_ac_coeffs(GetBitContext *gb, int16_t *out,
             return 0;
 
         run = decode_vlc_codeword(gb, ff_prores_ac_codebook[run_cb_index]);
+        if (run < 0)
+            return AVERROR_INVALIDDATA;
 
         bits_left = get_bits_left(gb);
         if (bits_left <= 0 || (bits_left <= 8 && !show_bits(gb, bits_left)))
             return AVERROR_INVALIDDATA;
 
         level = decode_vlc_codeword(gb, ff_prores_ac_codebook[lev_cb_index]) + 1;
+        if (level < 0)
+            return AVERROR_INVALIDDATA;
 
         pos += run + 1;
         if (pos >= max_coeffs)