Panic in gocql.marshalVarchar

[YeminLi]

What version of Scylla or Cassandra are you using?

3.0.7-0.20190528.4c16c1fe1

What version of Gocql are you using?

commit id = "91173a01ffb95ef90b31335d5cfc83eeda502a33"

What did you do?

call gocql get to get item

What did you expect to see?

no panic

What did you see instead?

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x461d2c]
	goroutine 709566504 [running]:
project/vendor/github.com/gocql/gocql.marshalVarchar(0x1b2d820, 0xc65b38a140, 0x149f340, 0xc68f1ada90, 0x0, 0xc09e53ce00, 0xc40ac045b0, 0xc40b95d7f0, 0xc40b95d7f8)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/marshal.go:214 +0x486
project/vendor/github.com/gocql/gocql.Marshal(0x1b2d820, 0xc65b38a140, 0x149f340, 0xc68f1ada90, 0x40e246, 0xc44a273bc0, 0x403b7f, 0xc40b95d940, 0xc40b95d880)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/marshal.go:68 +0x3b0
project/vendor/github.com/gocql/gocql.createRoutingKey(0xc478e904b0, 0xc68f1adaa0, 0x1, 0x1, 0xcc, 0xc478e904b0, 0x0, 0x0, 0x40f930)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/session.go:1732 +0xa7
project/vendor/github.com/gocql/gocql.(*Query).GetRoutingKey(0xc409867680, 0xc40b95d948, 0x4416f3, 0x149c9c0, 0xc06c0, 0x144f6c0)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/session.go:991 +0xf7
project/vendor/github.com/gocql/gocql.(*tokenAwareHostPolicy).Pick(0xc06d59c690, 0x1b42ca0, 0xc409867680, 0xc40b95da90)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/policies.go:591 +0x52
project/vendor/github.com/gocql/gocql.(*queryExecutor).do(0xc25968ea60, 0x1b2c860, 0xc4ab375c80, 0x1b42ca0, 0xc409867680, 0xb)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/query_executor.go:87 +0x63
project/vendor/github.com/gocql/gocql.(*queryExecutor).executeQuery(0xc25968ea60, 0x1b42ca0, 0xc409867680, 0x0, 0x0, 0x0)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/query_executor.go:60 +0x437
project/vendor/github.com/gocql/gocql.(*Session).executeQuery(0xc02c857c00, 0xc409867680, 0x17c3991)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/session.go:407 +0xb7
project/vendor/github.com/gocql/gocql.(*Query).Iter(0xc409867680, 0x28)
    /home/user/go/src/project/vendor/github.com/gocql/gocql/session.go:1110 +0xa5
project/vendor/github.com/scylladb/gocqlx.Iter(...)
    /home/user/go/src/project/vendor/github.com/scylladb/gocqlx/iterx.go:46
project/vendor/github.com/scylladb/gocqlx.(*Queryx).Get(0xc40b95de20, 0x1593d20, 0xc40880a9a0, 0x179b3e0, 0xc02c857c00)
    /home/user/go/src/project/vendor/github.com/scylladb/gocqlx/queryx.go:212 +0x70
project/vendor/github.com/scylladb/gocqlx.(*Queryx).GetRelease(0xc40b95de20, 0x1593d20, 0xc40880a9a0, 0x0, 0x0)
    /home/user/go/src/project/vendor/github.com/scylladb/gocqlx/queryx.go:219 +0x84

---

If you are having connectivity related issues please share the following additional information

Describe your Cassandra cluster

please provide the following information

• output of nodetool status
• output of SELECT peer, rpc_address FROM system.peers
• rebuild your application with the gocql_debug tag and post the output

[mmatczuk]

Hi, can you reproduce that? Can you reproduce that with the latest release 1.3.0?

[YeminLi]

Hi, can you reproduce that? Can you reproduce that with the latest release 1.3.0?

Yes, it also happens. With either version, it's not often.

[dahankzter]

What about with the latest 1.3.4?

I really have a very hard time getting how this could happen. Do you have a snippet of code and table structure that can reproduce this?

[mmatczuk]

Hi @YeminLi could you add information about Go version you use and what are you trying to marshal. A reproducer would be best. Thanks.

[sitano]

reproducer of failing at []byte(s):

package main

import (
	"fmt"
	"reflect"
	"unsafe"
)

func f(value interface{}) []byte {
	switch v := value.(type) {
	case string:
		return []byte(v) // <-- panics here
	}
	return nil
}

func main() {
	var s = "b"
	(*reflect.StringHeader)(unsafe.Pointer(&s)).Data = 0
	fmt.Println(f(s))
}

$ go run main.go
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x45ccc2]

goroutine 1 [running]:
main.f(0x49fb20, 0xc000072f68, 0xc000072f48, 0x43dc7a, 0x54ee20)
	/home/sitano/Projects/siren/1/main.go:12 +0x80
main.main()
	/home/sitano/Projects/siren/1/main.go:20 +0x6c
exit status 2

the string is broken and runtime.stringtoslicebyte fails

[sitano]

https://godbolt.org/z/N9cpt3 it can be seen that []byte(v) uses runtime function to convert from string

[dahankzter]

Can you provide a small example where it happens using the driver @YeminLi?

[YeminLi]

It happens when I'm doing a database read.

q := d.session.Query(getStmt).Consistency(gocql.One).Bind(key)
if err := gocqlx.Query(q, nil).WithContext(ctx).GetRelease(&object); err != nil {
    ...
}

Sorry I'm no able to provide any more useful information because it rarely happens and I don't see it happening recently...