panic: runtime error: invalid memory address or nil pointer dereference

[Felipe Reyes]

openstack.yaml -> http://paste.ubuntu.com/p/3PKTJXSzcR/
neutron-gateway.yaml -> http://paste.ubuntu.com/p/nbbZtCvghC/

$ snap info juju
...
installed: 2.7-beta1+develop-0f9f607 (8807) 75MB classic
$ juju --version
2.7-beta1-disco-amd64
$ juju deploy ./b/lp1680531/openstack.yaml --overlay ./b/lp1680531/o/neutron-gateway.yaml

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x98 pc=0x8e5b0c]

goroutine 1 [running]:
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200, 0x0, 0x0, 0x0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:185 +0xbc
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitFieldsInMap(0xc420241200, 0x2bc5ca0, 0xc420974900, 0x15, 0x15)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:212 +0x1ae
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200, 0x2bc5ca0, 0xc420974900, 0x2bc5ca0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:189 +0x1dc
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.VerifyNoOverlayFieldsPresent.func1(0xc420241200, 0x3135680, 0xc42095d450, 0x199, 0x36f3200, 0x3135680, 0x1)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:127 +0x2c6
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200, 0x299d5c0, 0xc42095d450, 0x299d5c0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:187 +0x12e
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitFieldsInMap(0xc420241200, 0x2bb92e0, 0xc420974750, 0x15, 0x15)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:212 +0x1ae
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200, 0x2bb92e0, 0xc420974750, 0x2bb92e0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:189 +0x1dc
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.VerifyNoOverlayFieldsPresent.func1(0xc420241200, 0x3094da0, 0xc42010e780, 0x199, 0x36f3200, 0x3094da0, 0x0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:127 +0x2c6
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200, 0x2f23d40, 0xc42010e780, 0x8)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:187 +0x12e
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.VerifyNoOverlayFieldsPresent(0xc42010e780, 0xc4201b92d8, 0x1)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:142 +0x16b
github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.ReadAndMergeBundleData(0xc4202411a0, 0x2, 0x2, 0x1, 0x2, 0xc4202411a0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:422 +0x300
github.com/juju/juju/cmd/juju/application.composeAndVerifyBundle(0x3684a60, 0xc4209750b0, 0xc4205e79e0, 0x1, 0x1, 0x0, 0x7, 0xc420d13601)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/juju/application/bundle.go:134 +0x25d
github.com/juju/juju/cmd/juju/application.(*DeployCommand).deployBundle(0xc4204182c0, 0xc4202b3040, 0x0, 0x3684a60, 0xc4209750b0, 0x0, 0x0, 0x0, 0xc4205e79e0, 0x1, ...)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/juju/application/deploy.go:897 +0x397
github.com/juju/juju/cmd/juju/application.(*DeployCommand).maybeReadLocalBundle.func1(0xc4202b3040, 0x3701f20, 0xc4202a82a0, 0xc420240220, 0x0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/juju/application/deploy.go:1363 +0x195
github.com/juju/juju/cmd/juju/application.(*DeployCommand).Run(0xc4204182c0, 0xc4202b3040, 0x0, 0x0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/juju/application/deploy.go:1223 +0x49a
github.com/juju/juju/cmd/modelcmd.(*modelCommandWrapper).Run(0xc4203897a0, 0xc4202b3040, 0xc4203897a0, 0xc420975c50)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/modelcmd/modelcommand.go:606 +0x11c
github.com/juju/juju/cmd/modelcmd.(*baseCommandWrapper).Run(0xc420222330, 0xc4202b3040, 0x0, 0x0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/modelcmd/base.go:471 +0xab
github.com/juju/juju/vendor/github.com/juju/cmd.(*SuperCommand).Run(0xc42022c8c0, 0xc4202b3040, 0xc4202b3040, 0x0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/github.com/juju/cmd/supercommand.go:516 +0x2cc
github.com/juju/juju/vendor/github.com/juju/cmd.Main(0x36a3020, 0xc42022c8c0, 0xc4202b3040, 0xc4200e8100, 0x4, 0x4, 0x2de89e0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/vendor/github.com/juju/cmd/cmd.go:379 +0x2d9
github.com/juju/juju/cmd/juju/commands.main.Run(0x3366618, 0xc4200e80f0, 0x5, 0x5, 0x0)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/juju/commands/main.go:143 +0x1af
github.com/juju/juju/cmd/juju/commands.Main(0xc4200e80f0, 0x5, 0x5, 0xc4200d4120)
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/juju/commands/main.go:89 +0x4b
main.main()
 /build/juju/parts/juju/go/src/github.com/juju/juju/cmd/juju/main.go:37 +0x8c

[Felipe Reyes (freyes)]

downgrading the client to the one in the candidate channel make things work again.

[Tim McNamara (tim-clicks)]

Thanks for reporting this issue Filipe. Could you please switch the channel
to 2.6/stable and let us know if it's also an issue there?

On Fri, 23 Aug 2019 at 08:20, Felipe Reyes <email address hidden>
wrote:

> Public bug reported:
>
>
> openstack.yaml -> http://paste.ubuntu.com/p/3PKTJXSzcR/
> neutron-gateway.yaml -> http://paste.ubuntu.com/p/nbbZtCvghC/
>
> $ snap info juju
> ...
> installed: 2.7-beta1+develop-0f9f607 (8807) 75MB classic
> $ juju --version
> 2.7-beta1-disco-amd64
> $ juju deploy ./b/lp1680531/openstack.yaml --overlay
> ./b/lp1680531/o/neutron-gateway.yaml
>
> panic: runtime error: invalid memory address or nil pointer dereference
> [signal SIGSEGV: segmentation violation code=0x1 addr=0x98 pc=0x8e5b0c]
>
> goroutine 1 [running]:
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200,
> 0x0, 0x0, 0x0)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:185 +0xbc
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitFieldsInMap(0xc420241200,
> 0x2bc5ca0, 0xc420974900, 0x15, 0x15)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:212 +0x1ae
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200,
> 0x2bc5ca0, 0xc420974900, 0x2bc5ca0)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:189 +0x1dc
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.VerifyNoOverlayFieldsPresent.func1(0xc420241200,
> 0x3135680, 0xc42095d450, 0x199, 0x36f3200, 0x3135680, 0x1)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:127 +0x2c6
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200,
> 0x299d5c0, 0xc42095d450, 0x299d5c0)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:187 +0x12e
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitFieldsInMap(0xc420241200,
> 0x2bb92e0, 0xc420974750, 0x15, 0x15)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:212 +0x1ae
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200,
> 0x2bb92e0, 0xc420974750, 0x2bb92e0)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:189 +0x1dc
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.VerifyNoOverlayFieldsPresent.func1(0xc420241200,
> 0x3094da0, 0xc42010e780, 0x199, 0x36f3200, 0x3094da0, 0x0)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:127 +0x2c6
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.visitField(0xc420241200,
> 0x2f23d40, 0xc42010e780, 0x8)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm.v6/overlay.go:187 +0x12e
>
> github.com/juju/juju/vendor/gopkg.in/juju/charm%2ev6.VerifyNoOverlayFieldsPresent(0xc42010e780,
> 0xc4201b92d8, 0x1)
> /build/juju/parts/juju/go/src/
> github.com/juju/juju/vendor/gopkg.in/juju/charm...

[Felipe Reyes (freyes)]

On Thu, 2019-08-22 at 20:37 +0000, Tim McNamara wrote:
> Thanks for reporting this issue Filipe. Could you please switch the
> channel
> to 2.6/stable and let us know if it's also an issue there?

with 2.6.6. there are no errors.

[John A Meinel (jameinel)]

The code in question is:
// visitField invokes ctx.structVisitor(val) if v is a struct and returns back
// the visitor's result. On the other hand, if val is a slice or a map,
// visitField invoke specialized functions that support iterating such types.
func visitField(ctx *visitorContext, val interface{}) bool {
        typ := reflect.TypeOf(val)
        v := reflect.ValueOf(val)

        // De-reference pointers
        if v.Kind() == reflect.Ptr {
                v = v.Elem()
                if v.Kind() == reflect.Invalid {
                        return false
                }
                typ = v.Type()
        }

        switch typ.Kind() {
        case reflect.Struct:
                return ctx.structVisitor(ctx, v, typ)
        case reflect.Map:
                return visitFieldsInMap(ctx, v)
        case reflect.Slice:
                return visitFieldsInSlice(ctx, v)
        }

        // v is not a struct or something we can iterate to reach a struct
        return false
}

But the docs:
https://golang.org/pkg/reflect/#TypeOf

say that reflect.TypeOf(nil) => nil, thus the later call to typ.Kind() is an invalid call.

I don't know what value in the bundle would point to nil, but regardless we can have code that is defensive against nil values.

[Achilleas Anagnostopoulos (achilleasa)]

The attached base bundle defines the following set of variables:

# Variables
debug: &debug True
verbose: &verbose True
openstack_origin: &openstack_origin cloud:bionic-rocky
source: &source cloud:bionic-rocky
num_compute_units: &num_compute_units 1

ssl_ca: &ssl_ca
ssl_cert: &ssl_cert
ssl_key: &ssl_key

The ssl_* ones (which are defined to null in the above snippet) are referenced in the nova-cloud-controller app from the base bundle:

 nova-cloud-controller:
    num_units: 1
    charm: cs:~openstack-charmers-next/nova-cloud-controller
    constraints: mem=2G
    options:
      debug: *debug
      verbose: *verbose
      network-manager: Neutron
      openstack-origin: *openstack_origin
      ssl_ca: *ssl_ca
      ssl_cert: *ssl_cert
      ssl_key: *ssl_key

This causes a nil value to be passed into "visitField" which triggers the panic. Adding a check for nil values in the top of that function resolves the issue. I will push a PR with a fix.

[Achilleas Anagnostopoulos (achilleasa)]

PR https://github.com/juju/juju/pull/10565 includes a fix for the develop branch. Note, this issue does not affect the 2.6 line as this particular codepath is only used by the develop branch.

[John A Meinel (jameinel)]

Marking this fix released as it should be picked up in the next Edge build.