avcodec/hevc_ps: Check delta_pocs in ff_hevc_decode_short_term_rps()

Fixes: integer overflow
Fixes: 2893/clusterfuzz-testcase-minimized-5809330567774208

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/hevc_ps.c

@@ -225,6 +225,12 @@ int ff_hevc_decode_short_term_rps(GetBitContext *gb, AVCodecContext *avctx,
             prev = 0;
             for (i = 0; i < rps->num_negative_pics; i++) {
                 delta_poc = get_ue_golomb_long(gb) + 1;
+                if (delta_poc < 1 || delta_poc > 32768) {
+                    av_log(avctx, AV_LOG_ERROR,
+                        "Invalid value of delta_poc: %d\n",
+                        delta_poc);
+                    return AVERROR_INVALIDDATA;
+                }
                 prev -= delta_poc;
                 rps->delta_poc[i] = prev;
                 rps->used[i]      = get_bits1(gb);
@@ -232,6 +238,12 @@ int ff_hevc_decode_short_term_rps(GetBitContext *gb, AVCodecContext *avctx,
             prev = 0;
             for (i = 0; i < nb_positive_pics; i++) {
                 delta_poc = get_ue_golomb_long(gb) + 1;
+                if (delta_poc < 1 || delta_poc > 32768) {
+                    av_log(avctx, AV_LOG_ERROR,
+                        "Invalid value of delta_poc: %d\n",
+                        delta_poc);
+                    return AVERROR_INVALIDDATA;
+                }
                 prev += delta_poc;
                 rps->delta_poc[rps->num_negative_pics + i] = prev;
                 rps->used[rps->num_negative_pics + i]      = get_bits1(gb);