Mempool tx.Hash nil pointer dereference in frontend/service.go:480

[skyl]

lightwalletd crashed a few times. Restarting seems to get it going again and it's running again for now.

This is on mainnet with the debian 5.1.0 release of zcashd and db2795a version of lightwalletd.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x38 pc=0xa1009c]

goroutine 133 [running]:
github.com/zcash/lightwalletd/frontend.(*lwdStreamer).GetMempoolTx(0xc00000f7a0, 0xc000d86500, {0xd513e0, 0xc0002688f0})
	free2z/zcash/lightwalletd/frontend/service.go:480 +0x3fc
github.com/zcash/lightwalletd/walletrpc._CompactTxStreamer_GetMempoolTx_Handler({0xb51a00, 0xc0014f1340}, {0xd4de80, 0xc00000f7a0})
	free2z/zcash/lightwalletd/walletrpc/service_grpc.pb.go:632 +0xd0
github.com/grpc-ecosystem/go-grpc-prometheus.(*ServerMetrics).StreamServerInterceptor.func1({0xb51a00, 0xc0014f1340}, {0xd4dfa0, 0xc00024a5b0}, 0x8, 0xc85fb0)
	go/pkg/mod/github.com/grpc-ecosystem/[email protected]/server_metrics.go:121 +0x109
github.com/grpc-ecosystem/go-grpc-middleware.ChainStreamServer.func1.1.1({0xb51a00, 0xc0014f1340}, {0xd4dfa0, 0xc00024a5b0})
	go/pkg/mod/github.com/grpc-ecosystem/[email protected]/chain.go:49 +0x3a
github.com/grpc-ecosystem/go-grpc-middleware.ChainStreamServer.func1({0xb51a00, 0xc0014f1340}, {0xd4dfa0, 0xc00024a5b0}, 0xa5eae0, 0xc0002688e0)
	go/pkg/mod/github.com/grpc-ecosystem/[email protected]/chain.go:58 +0xbf
google.golang.org/grpc.(*Server).processStreamingRPC(0xc000238540, {0xd54568, 0xc000285a00}, 0xc000263b00, 0xc0002a3170, 0x11f2c00, 0x0)
	go/pkg/mod/google.golang.org/[email protected]/server.go:1549 +0xe8e
google.golang.org/grpc.(*Server).handleStream(0xc000238540, {0xd54568, 0xc000285a00}, 0xc000263b00, 0x0)
	go/pkg/mod/google.golang.org/[email protected]/server.go:1624 +0x9e5
google.golang.org/grpc.(*Server).serveStreams.func1.2()
	go/pkg/mod/google.golang.org/[email protected]/server.go:922 +0x98
created by google.golang.org/grpc.(*Server).serveStreams.func1
	go/pkg/mod/google.golang.org/[email protected]/server.go:920 +0x294

I haven't looked into it yet but it's the tx.Hash in:

	for _, txid := range MempoolFilter(mempoolList, excludeHex) {
		tx := (*mempoolMap)[txid]
		if len(tx.Hash) > 0 {

[skyl]

happened again, I think that makes 5 times in about an hour after not happening for 24 hours ... zcashd seems to be running fine .. although some logging I'm not familiar with happened at the same time

2022-07-11T03:30:41.503203Z  INFO main: keypool reserve 1
2022-07-11T03:30:41.503255Z  INFO main: keypool return 1
2022-07-11T03:30:48.750634Z  INFO main: keypool reserve 1
2022-07-11T03:30:48.750699Z  INFO main: keypool return 1

[LarryRuane]

Thanks for the report! This will be fixed by #403, awaiting review. The failure isn't exactly dereferencing a nil pointer, it's indexing a Go map using a nonexistent key. We should have this fixed within a few days.

While investigating this problem, I discovered that this gRPC, GetMempoolTx, isn't returning any entries at all. This will be fixed by #404.