CVE-2023-53987 ping: Fix potentail NULL deref for /proc/net/icmp.

[
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    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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      "net/ipv4/ping.c"
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    ]
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    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "net/ipv4/ping.c"
    ],
    "versions": [
      {
        "version": "6.0",
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      {
        "version": "0",
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      {
        "version": "6.1.24",
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      {
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      {
        "version": "6.3",
        "lessThanOrEqual": "*",
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]