Quadlet: Invalid Mount directive leads to core dump

[mhutter]

Issue Description

*.container files with invalid Mount directives will cause quadlet to crash, instead of outputting an error message

Steps to reproduce the issue

Given the following /etc/containers/systemd/prometheus.container

# ...
[Container]
Mount=/etc/prometheus.yml:/prometheus.yml:ro

Running /usr/libexec/podman/quadlet -dryrun

Describe the results you received

panic: runtime error: index out of range [1] with length 1

goroutine 1 [running]:
panic({0x5619b51f3c40, 0xc00001c150})
        /usr/lib/golang/src/runtime/panic.go:987 +0x3bb fp=0xc0000bb1e8 sp=0xc0000bb128 pc=0x5619b510a0bb
runtime.goPanicIndex(0x1, 0x1)
        /usr/lib/golang/src/runtime/panic.go:113 +0x7f fp=0xc0000bb228 sp=0xc0000bb1e8 pc=0x5619b510845f
github.com/containers/podman/v4/pkg/systemd/quadlet.ConvertContainer(0xc00005c380, 0x20?)
        /builddir/build/BUILD/podman-4.6.2/pkg/systemd/quadlet/quadlet.go:641 +0x4fe5 fp=0xc0000bbc48 sp=0xc0000bb228 pc=0x5619b51a5125
main.process()
        /builddir/build/BUILD/podman-4.6.2/cmd/quadlet/main.go:395 +0x833 fp=0xc0000bbf38 sp=0xc0000bbc48 pc=0x5619b51ad7f3
main.main()
        /builddir/build/BUILD/podman-4.6.2/cmd/quadlet/main.go:316 +0x19 fp=0xc0000bbf80 sp=0xc0000bbf38 pc=0x5619b51acf39
runtime.main()
        /usr/lib/golang/src/runtime/proc.go:250 +0x212 fp=0xc0000bbfe0 sp=0xc0000bbf80 pc=0x5619b510ce32
runtime.goexit()
        /usr/lib/golang/src/runtime/asm_amd64.s:1598 +0x1 fp=0xc0000bbfe8 sp=0xc0000bbfe0 pc=0x5619b5138821

Describe the results you expected

A helpful error message

podman info output

host:
  arch: amd64
  buildahVersion: 1.31.2
  cgroupControllers:
  - cpuset
  - cpu
  - io
  - memory
  - hugetlb
  - pids
  - rdma
  - misc
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: conmon-2.1.7-2.fc38.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.1.7, commit: '
  cpuUtilization:
    idlePercent: 98.33
    systemPercent: 0.71
    userPercent: 0.96
  cpus: 1
  databaseBackend: boltdb
  distribution:
    distribution: fedora
    variant: coreos
    version: "38"
  eventLogger: journald
  freeLocks: 2047
  hostname: my-first-coreos
  idMappings:
    gidmap: null
    uidmap: null
  kernel: 6.4.15-200.fc38.x86_64
  linkmode: dynamic
  logDriver: journald
  memFree: 1350725632
  memTotal: 1998385152
  networkBackend: netavark
  networkBackendInfo:
    backend: netavark
    dns:
      package: aardvark-dns-1.7.0-1.fc38.x86_64
      path: /usr/libexec/podman/aardvark-dns
      version: aardvark-dns 1.7.0
    package: netavark-1.7.0-1.fc38.x86_64
    path: /usr/libexec/podman/netavark
    version: netavark 1.7.0
  ociRuntime:
    name: crun
    package: crun-1.8.7-1.fc38.x86_64
    path: /usr/bin/crun
    version: |-
      crun version 1.8.7
      commit: 53a9996ce82d1ee818349bdcc64797a1fa0433c4
      rundir: /run/crun
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +LIBKRUN +WASM:wasmedge +YAJL
  os: linux
  pasta:
    executable: /usr/bin/pasta
    package: passt-0^20230823.ga7e4bfb-1.fc38.x86_64
    version: |
      pasta 0^20230823.ga7e4bfb-1.fc38.x86_64
      Copyright Red Hat
      GNU Affero GPL version 3 or later <https://www.gnu.org/licenses/agpl-3.0.html>
      This is free software: you are free to change and redistribute it.
      There is NO WARRANTY, to the extent permitted by law.
  remoteSocket:
    path: /run/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: false
    seccompEnabled: true
    seccompProfilePath: /usr/share/containers/seccomp.json
    selinuxEnabled: true
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.2.1-1.fc38.x86_64
    version: |-
      slirp4netns version 1.2.1
      commit: 09e31e92fa3d2a1d3ca261adaeb012c8d75a8194
      libslirp: 4.7.0
      SLIRP_CONFIG_VERSION_MAX: 4
      libseccomp: 2.5.3
  swapFree: 0
  swapTotal: 0
  uptime: 1h 8m 32.00s (Approximately 0.04 days)
plugins:
  authorization: null
  log:
  - k8s-file
  - none
  - passthrough
  - journald
  network:
  - bridge
  - macvlan
  - ipvlan
  volume:
  - local
registries:
  search:
  - registry.fedoraproject.org
  - registry.access.redhat.com
  - docker.io
  - quay.io
store:
  configFile: /usr/share/containers/storage.conf
  containerStore:
    number: 1
    paused: 0
    running: 1
    stopped: 0
  graphDriverName: overlay
  graphOptions:
    overlay.mountopt: nodev,metacopy=on
  graphRoot: /var/lib/containers/storage
  graphRootAllocated: 19875737600
  graphRootUsed: 1675010048
  graphStatus:
    Backing Filesystem: xfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "true"
  imageCopyTmpDir: /var/tmp
  imageStore:
    number: 1
  runRoot: /run/containers/storage
  transientStore: false
  volumePath: /var/lib/containers/storage/volumes
version:
  APIVersion: 4.6.2
  Built: 1693251588
  BuiltTime: Mon Aug 28 19:39:48 2023
  GitCommit: ""
  GoVersion: go1.20.7
  Os: linux
  OsArch: linux/amd64
  Version: 4.6.2

Podman in a container

No

Privileged Or Rootless

None

Upstream Latest Release

Yes

Additional environment details

CoreOS

Additional information

No response

[mhutter]

I think I can fix this, assign it to me if I should prepare a PR