GHSA-9PCQ-FQFF-43QC

Vulnerability from github – Published: 2025-03-27 15:31 – Updated: 2025-11-03 21:33
VLAI?
Details

In the Linux kernel, the following vulnerability has been resolved:

efi: Don't map the entire mokvar table to determine its size

Currently, when validating the mokvar table, we (re)map the entire table on each iteration of the loop, adding space as we discover new entries. If the table grows over a certain size, this fails due to limitations of early_memmap(), and we get a failure and traceback:

------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at mm/early_ioremap.c:139 __early_ioremap+0xef/0x220 ... Call Trace: ? __early_ioremap+0xef/0x220 ? __warn.cold+0x93/0xfa ? __early_ioremap+0xef/0x220 ? report_bug+0xff/0x140 ? early_fixup_exception+0x5d/0xb0 ? early_idt_handler_common+0x2f/0x3a ? __early_ioremap+0xef/0x220 ? efi_mokvar_table_init+0xce/0x1d0 ? setup_arch+0x864/0xc10 ? start_kernel+0x6b/0xa10 ? x86_64_start_reservations+0x24/0x30 ? x86_64_start_kernel+0xed/0xf0 ? common_startup_64+0x13e/0x141 ---[ end trace 0000000000000000 ]--- mokvar: Failed to map EFI MOKvar config table pa=0x7c4c3000, size=265187.

Mapping the entire structure isn't actually necessary, as we don't ever need more than one entry header mapped at once.

Changes efi_mokvar_table_init() to only map each entry header, not the entire table, when determining the table size. Since we're not mapping any data past the variable name, it also changes the code to enforce that each variable name is NUL terminated, rather than attempting to verify it in place.

Severity ?
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2025-21872"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-03-27T15:15:54Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nefi: Don\u0027t map the entire mokvar table to determine its size\n\nCurrently, when validating the mokvar table, we (re)map the entire table\non each iteration of the loop, adding space as we discover new entries.\nIf the table grows over a certain size, this fails due to limitations of\nearly_memmap(), and we get a failure and traceback:\n\n  ------------[ cut here ]------------\n  WARNING: CPU: 0 PID: 0 at mm/early_ioremap.c:139 __early_ioremap+0xef/0x220\n  ...\n  Call Trace:\n   \u003cTASK\u003e\n   ? __early_ioremap+0xef/0x220\n   ? __warn.cold+0x93/0xfa\n   ? __early_ioremap+0xef/0x220\n   ? report_bug+0xff/0x140\n   ? early_fixup_exception+0x5d/0xb0\n   ? early_idt_handler_common+0x2f/0x3a\n   ? __early_ioremap+0xef/0x220\n   ? efi_mokvar_table_init+0xce/0x1d0\n   ? setup_arch+0x864/0xc10\n   ? start_kernel+0x6b/0xa10\n   ? x86_64_start_reservations+0x24/0x30\n   ? x86_64_start_kernel+0xed/0xf0\n   ? common_startup_64+0x13e/0x141\n   \u003c/TASK\u003e\n  ---[ end trace 0000000000000000 ]---\n  mokvar: Failed to map EFI MOKvar config table pa=0x7c4c3000, size=265187.\n\nMapping the entire structure isn\u0027t actually necessary, as we don\u0027t ever\nneed more than one entry header mapped at once.\n\nChanges efi_mokvar_table_init() to only map each entry header, not the\nentire table, when determining the table size.  Since we\u0027re not mapping\nany data past the variable name, it also changes the code to enforce\nthat each variable name is NUL terminated, rather than attempting to\nverify it in place.",
  "id": "GHSA-9pcq-fqff-43qc",
  "modified": "2025-11-03T21:33:13Z",
  "published": "2025-03-27T15:31:10Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21872"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2b90e7ace79774a3540ce569e000388f8d22c9e0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/46c0454ffb78ce9d3355a3cccac86383ea8ddd55"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/65f4aebb8127708ba668dd938e83b8558abfc5cd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/97bd560b6cc4c26386a53b4881bf03e96f9ba03a"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ea3f0b362dfe4ef885ef812bfaf4088176422c91"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}


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