remove mem leak in error cases, for example on error by write or if i…

…t was cut or by partial extraction (no return without free, done list may contain not processed entries, so library leaks);

+ small code deduplication

C/zstdmt/brotli-mt_decompress.c

@@ -363,12 +363,7 @@ static void *pt_decompress(void *arg)
 	}
 
 	/* everything is okay */
-	pthread_mutex_lock(&ctx->write_mutex);
-	list_move(&wl->node, &ctx->writelist_free);
-	pthread_mutex_unlock(&ctx->write_mutex);
-	if (in->allocated)
-		free(in->buf);
-	return 0;
+	result = 0;
 
  error_lock:
 	pthread_mutex_lock(&ctx->write_mutex);
@@ -508,8 +503,8 @@ size_t BROTLIMT_decompressDCtx(BROTLIMT_DCtx * ctx, BROTLIMT_RdWr_t * rdwr)
 		/* no pthread_create() needed! */
 		void *p = pt_decompress(w);
 		if (p)
-			return (size_t) p;
-		goto okay;
+			retval_of_thread = p;
+		goto done;
 	}
 
 	/* multi threaded */
@@ -530,7 +525,16 @@ size_t BROTLIMT_decompressDCtx(BROTLIMT_DCtx * ctx, BROTLIMT_RdWr_t * rdwr)
 			retval_of_thread = p;
 	}
 
- okay:
+ done:
+	/* move remaining done/busy entries to free list */
+	while (!list_empty(&ctx->writelist_done)) {
+		struct list_head *entry = list_first(&ctx->writelist_done);
+		list_move(entry, &ctx->writelist_free);
+	}
+	while (!list_empty(&ctx->writelist_busy)) {
+		struct list_head* entry = list_first(&ctx->writelist_busy);
+		list_move(entry, &ctx->writelist_free);
+	}
 	/* clean up the buffers */
 	while (!list_empty(&ctx->writelist_free)) {
 		struct writelist *wl;