avcodec/hevcdec: Check nb_sps

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/hevcdec.c

@@ -248,6 +248,8 @@ static int decode_lt_rps(HEVCContext *s, LongTermRPS *rps, GetBitContext *gb)
         nb_sps = get_ue_golomb_long(gb);
     nb_sh = get_ue_golomb_long(gb);
 
+    if (nb_sps > sps->num_long_term_ref_pics_sps)
+        return AVERROR_INVALIDDATA;
     if (nb_sh + (uint64_t)nb_sps > FF_ARRAY_ELEMS(rps->poc))
         return AVERROR_INVALIDDATA;