Adding filtering host events as described in Hello world gadget tutorial causes segmentation violation

[Sefi4]

Description

I followed the hello world gadget tutorial as described here: https://www.inspektor-gadget.io/docs/latest/devel/hello-world-gadget/.

Everything worked fine, until getting to "Filtering and container enrichement" section:
https://www.inspektor-gadget.io/docs/latest/devel/hello-world-gadget/#filtering-and-container-enrichement
(BTW there's a typo in the section title it should be enrichment instead of enrichement).

When adding the host filtering part as described in the tutorial I receive the following error:
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x20720bd]

goroutine 1 [running]:
github.com/inspektor-gadget/inspektor-gadget/pkg/operators/localmanager.(*localManagerTraceWrapper).PreStart(0xc003992080, {0x2d8c008, 0xc0030f9c80})
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/operators/localmanager/localmanager.go:532 +0xbd
github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context.(*GadgetContext).run(0xc0030f9c80, {0xc0031cf1d0, 0x3, 0x17?})
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context/run.go:103 +0x197
github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context.(*GadgetContext).Run(0xc0030f9c80, 0xc000050f40?)
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context/run.go:167 +0x9e
github.com/inspektor-gadget/inspektor-gadget/pkg/runtime/local.(*Runtime).RunGadget(0x22d4f60?, {0x2db2d60?, 0xc0030f9c80?}, 0xd?, 0xc002af5b80?)
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/runtime/local/oci.go:35 +0x27
github.com/inspektor-gadget/inspektor-gadget/cmd/common.NewRunCommand.func2(0xc00039c608, {0xc00037f440?, 0x2?, 0x2?})
/go/src/github.com/inspektor-gadget/inspektor-gadget/cmd/common/oci.go:180 +0x6d7
github.com/spf13/cobra.(*Command).execute(0xc00039c608, {0xc00037f440, 0x2, 0x2})
/go/pkg/mod/github.com/spf13/[email protected]/command.go:983 +0xaca
github.com/spf13/cobra.(*Command).ExecuteC(0xc0004f6908)
/go/pkg/mod/github.com/spf13/[email protected]/command.go:1115 +0x3ff
github.com/spf13/cobra.(*Command).Execute(...)
/go/pkg/mod/github.com/spf13/[email protected]/command.go:1039
main.main()
/go/src/github.com/inspektor-gadget/inspektor-gadget/cmd/ig/main.go:91 +0x374

Impact

Can't add host filtering to hello world gadget.

Environment and steps to reproduce

1. Set-up: I use WSL with Docker Desktop v4.30.0.
2. Task: Adding the host filtering part to the hello world gadget (copy pasting from the tutorial).
3. Action(s): Follow the "Filtering and container enrichement" as described in: https://www.inspektor-gadget.io/docs/latest/devel/hello-world-gadget/#filtering-and-container-enrichement
4. Error: INFO[0000] Experimental features enabled
   WARN[0000] you set --verify-image=false, image will not be verified
   WARN[0000] failed to get cgroups info of container 3ebd135cf445cd857c2c42bf5a923b704de1106efa9a837c8206a2dcae5c8c0f from /proc/341/cgroup: parsing cgroup: open /proc/341/cgroup: no such file or directory
   WARN[0000] Failed to create container-collection
   WARN[0000] you set --verify-image=false, image will not be verified
   WARN[0000] failed to get cgroups info of container 3ebd135cf445cd857c2c42bf5a923b704de1106efa9a837c8206a2dcae5c8c0f from /proc/341/cgroup: parsing cgroup: open /proc/341/cgroup: no such file or directory
   WARN[0001] Failed to create container-collection
   panic: runtime error: invalid memory address or nil pointer dereference
   [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x20720bd]

goroutine 1 [running]:
github.com/inspektor-gadget/inspektor-gadget/pkg/operators/localmanager.(*localManagerTraceWrapper).PreStart(0xc003992080, {0x2d8c008, 0xc0030f9c80})
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/operators/localmanager/localmanager.go:532 +0xbd
github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context.(*GadgetContext).run(0xc0030f9c80, {0xc0031cf1d0, 0x3, 0x17?})
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context/run.go:103 +0x197
github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context.(*GadgetContext).Run(0xc0030f9c80, 0xc000050f40?)
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context/run.go:167 +0x9e
github.com/inspektor-gadget/inspektor-gadget/pkg/runtime/local.(*Runtime).RunGadget(0x22d4f60?, {0x2db2d60?, 0xc0030f9c80?}, 0xd?, 0xc002af5b80?)
/go/src/github.com/inspektor-gadget/inspektor-gadget/pkg/runtime/local/oci.go:35 +0x27
github.com/inspektor-gadget/inspektor-gadget/cmd/common.NewRunCommand.func2(0xc00039c608, {0xc00037f440?, 0x2?, 0x2?})
/go/src/github.com/inspektor-gadget/inspektor-gadget/cmd/common/oci.go:180 +0x6d7
github.com/spf13/cobra.(*Command).execute(0xc00039c608, {0xc00037f440, 0x2, 0x2})
/go/pkg/mod/github.com/spf13/[email protected]/command.go:983 +0xaca
github.com/spf13/cobra.(*Command).ExecuteC(0xc0004f6908)
/go/pkg/mod/github.com/spf13/[email protected]/command.go:1115 +0x3ff
github.com/spf13/cobra.(*Command).Execute(...)
/go/pkg/mod/github.com/spf13/[email protected]/command.go:1039
main.main()
/go/src/github.com/inspektor-gadget/inspektor-gadget/cmd/ig/main.go:91 +0x374

Expected behavior

The hello world gadget is ran as described in the tutorial.

Additional information

I'm running the image based gadget with --image-verify=false because of another issue I was experiencing with the tutorial:
#2872 (comment)

Please add any information here that does not fit the above format.

[mauriciovasquezbernal]

@Sefi4 thanks a lot for opening this issue. It'll be fixed by #2874.

In the mean time, if you want to continue experimenting you can install runc or docker or another container runtime.

[alban]

Set-up: I use WSL with Docker Desktop v4.30.0.

#2874 should fix the panic but you will need #2875 as well if you start ig directly from a WSL shell and not within a docker container.