avcodec/elsdec: Fix memleaks

Fixes: 6798/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_G2M_fuzzer-5135899701542912

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 0bd0401336)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/elsdec.c

@@ -271,7 +271,7 @@ void ff_els_decoder_init(ElsDecCtx *ctx, const uint8_t *in, size_t data_size)
 
 void ff_els_decoder_uninit(ElsUnsignedRung *rung)
 {
-    av_free(rung->rem_rung_list);
+    av_freep(&rung->rem_rung_list);
 }
 
 static int els_import_byte(ElsDecCtx *ctx)
@@ -391,12 +391,10 @@ unsigned ff_els_decode_unsigned(ElsDecCtx *ctx, ElsUnsignedRung *ur)
                 if (ur->rung_list_size <= (ur->avail_index + 2) * sizeof(ElsRungNode)) {
                     // remember rung_node position
                     ptrdiff_t pos     = rung_node - ur->rem_rung_list;
-                    ur->rem_rung_list = av_realloc(ur->rem_rung_list,
+                    ctx->err = av_reallocp(&ur->rem_rung_list,
                                                    ur->rung_list_size +
                                                    RUNG_SPACE);
-                    if (!ur->rem_rung_list) {
-                        av_free(ur->rem_rung_list);
-                        ctx->err = AVERROR(ENOMEM);
+                    if (ctx->err < 0) {
                         return 0;
                     }
                     memset((uint8_t *) ur->rem_rung_list + ur->rung_list_size, 0,

libavcodec/g2meet.c

@@ -927,6 +927,7 @@ static int epic_jb_decode_tile(G2MContext *c, int tile_x, int tile_y,
         if (c->ec.els_ctx.err != 0) {
             av_log(avctx, AV_LOG_ERROR,
                    "ePIC: couldn't decode transparency pixel!\n");
+            ff_els_decoder_uninit(&c->ec.unsigned_rung);
             return AVERROR_INVALIDDATA;
         }