spv: fix unsafe waitgroup usage

The goroutine started after receiving an inv also spawns its own goroutines
and increments the waitgroup counter.  This is invalid waitgroup usage as it
could occur concurrently with or after the call to Wait().  Removing the
superfluous outer goroutine fixes this issue.

Author: jrick

spv/sync.go

@@ -703,49 +703,43 @@ func (s *Syncer) receiveInv(ctx context.Context) error {
 			return err
 		}
 
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-
-			var blocks []*chainhash.Hash
-			var txs []*chainhash.Hash
-
-			for _, inv := range msg.InvList {
-				switch inv.Type {
-				case wire.InvTypeBlock:
-					blocks = append(blocks, &inv.Hash)
-				case wire.InvTypeTx:
-					txs = append(txs, &inv.Hash)
-				}
+		var blocks []*chainhash.Hash
+		var txs []*chainhash.Hash
+		for _, inv := range msg.InvList {
+			switch inv.Type {
+			case wire.InvTypeBlock:
+				blocks = append(blocks, &inv.Hash)
+			case wire.InvTypeTx:
+				txs = append(txs, &inv.Hash)
 			}
+		}
 
-			if len(blocks) != 0 {
-				wg.Add(1)
-				go func() {
-					defer wg.Done()
+		if len(blocks) != 0 {
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
 
-					err := s.handleBlockInvs(ctx, rp, blocks)
-					if ctx.Err() != nil {
-						return
-					}
-					if errors.Is(err, errors.Protocol) || errors.Is(err, errors.Consensus) {
-						log.Warnf("Disconnecting peer %v: %v", rp, err)
-						rp.Disconnect(err)
-						return
-					}
-					if err != nil {
-						log.Warnf("Failed to handle blocks inventoried by %v: %v", rp, err)
-					}
-				}()
-			}
-			if len(txs) != 0 {
-				wg.Add(1)
-				go func() {
-					s.handleTxInvs(ctx, rp, txs)
-					wg.Done()
-				}()
-			}
-		}()
+				err := s.handleBlockInvs(ctx, rp, blocks)
+				if ctx.Err() != nil {
+					return
+				}
+				if errors.Is(err, errors.Protocol) || errors.Is(err, errors.Consensus) {
+					log.Warnf("Disconnecting peer %v: %v", rp, err)
+					rp.Disconnect(err)
+					return
+				}
+				if err != nil {
+					log.Warnf("Failed to handle blocks inventoried by %v: %v", rp, err)
+				}
+			}()
+		}
+		if len(txs) != 0 {
+			wg.Add(1)
+			go func() {
+				s.handleTxInvs(ctx, rp, txs)
+				wg.Done()
+			}()
+		}
 	}
 }