Vulnerability-Lookup

GHSA-56RC-PFJ3-9MX3

Vulnerability from github – Published: 2025-12-04 18:30 – Updated: 2026-07-30 06:32

Details

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

nios2: ensure that memblock.current_limit is set when setting pfn limits

On nios2, with CONFIG_FLATMEM set, the kernel relies on memblock_get_current_limit() to determine the limits of mem_map, in particular for max_low_pfn. Unfortunately, memblock.current_limit is only default initialized to MEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading to situations where max_low_pfn can erroneously exceed the value of max_pfn and, thus, the valid range of available DRAM.

This can in turn cause kernel-level paging failures, e.g.:

[ 76.900000] Unable to handle kernel paging request at virtual address 20303000 [ 76.900000] ea = c0080890, ra = c000462c, cause = 14 [ 76.900000] Kernel panic - not syncing: Oops [ 76.900000] ---[ end Kernel panic - not syncing: Oops ]---

This patch fixes this by pre-calculating memblock.current_limit based on the upper limits of the available memory ranges via adjust_lowmem_bounds, a simplified version of the equivalent implementation within the arm architecture.

Severity

7.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2025-40245"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-12-04T16:16:17Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnios2: ensure that memblock.current_limit is set when setting pfn limits\n\nOn nios2, with CONFIG_FLATMEM set, the kernel relies on\nmemblock_get_current_limit() to determine the limits of mem_map, in\nparticular for max_low_pfn.\nUnfortunately, memblock.current_limit is only default initialized to\nMEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading\nto situations where max_low_pfn can erroneously exceed the value of\nmax_pfn and, thus, the valid range of available DRAM.\n\nThis can in turn cause kernel-level paging failures, e.g.:\n\n[   76.900000] Unable to handle kernel paging request at virtual address 20303000\n[   76.900000] ea = c0080890, ra = c000462c, cause = 14\n[   76.900000] Kernel panic - not syncing: Oops\n[   76.900000] ---[ end Kernel panic - not syncing: Oops ]---\n\nThis patch fixes this by pre-calculating memblock.current_limit\nbased on the upper limits of the available memory ranges via\nadjust_lowmem_bounds, a simplified version of the equivalent\nimplementation within the arm architecture.",
  "id": "GHSA-56rc-pfj3-9mx3",
  "modified": "2026-07-30T06:32:18Z",
  "published": "2025-12-04T18:30:52Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-40245"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/25f09699edd360b534ccae16bc276c3b52c471f3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5c3e38a367822f036227dd52bac82dc4a05157e2"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8912814f14e298b83df072fecc1f7ed1b63b1b2c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/90f5f715550e07cd6a51f80fc3f062d832c8c997"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a20b83cf45be2057f3d073506779e52c7fa17f94"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b1ec9faef7e36269ca3ec890972a78effbaeb975"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2025-40245 (GCVE-0-2025-40245)

Vulnerability from cvelistv5 – Published: 2025-12-04 15:31 – Updated: 2026-08-05 12:08

Title

nios2: ensure that memblock.current_limit is set when setting pfn limits

Summary

In the Linux kernel, the following vulnerability has been resolved: nios2: ensure that memblock.current_limit is set when setting pfn limits On nios2, with CONFIG_FLATMEM set, the kernel relies on memblock_get_current_limit() to determine the limits of mem_map, in particular for max_low_pfn. Unfortunately, memblock.current_limit is only default initialized to MEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading to situations where max_low_pfn can erroneously exceed the value of max_pfn and, thus, the valid range of available DRAM. This can in turn cause kernel-level paging failures, e.g.: [ 76.900000] Unable to handle kernel paging request at virtual address 20303000 [ 76.900000] ea = c0080890, ra = c000462c, cause = 14 [ 76.900000] Kernel panic - not syncing: Oops [ 76.900000] ---[ end Kernel panic - not syncing: Oops ]--- This patch fixes this by pre-calculating memblock.current_limit based on the upper limits of the available memory ranges via adjust_lowmem_bounds, a simplified version of the equivalent implementation within the arm architecture.

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7033 records in the last 180 days details

References

6 references

URL	Tags
https://git.kernel.org/stable/c/25f09699edd360b53…
https://git.kernel.org/stable/c/5c3e38a367822f036…
https://git.kernel.org/stable/c/b1ec9faef7e36269c…
https://git.kernel.org/stable/c/90f5f715550e07cd6…
https://git.kernel.org/stable/c/8912814f14e298b83…
https://git.kernel.org/stable/c/a20b83cf45be2057f…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 25f09699edd360b534ccae16bc276c3b52c471f3 (git) Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 5c3e38a367822f036227dd52bac82dc4a05157e2 (git) Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < b1ec9faef7e36269ca3ec890972a78effbaeb975 (git) Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 90f5f715550e07cd6a51f80fc3f062d832c8c997 (git) Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < 8912814f14e298b83df072fecc1f7ed1b63b1b2c (git) Affected: 7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae , < a20b83cf45be2057f3d073506779e52c7fa17f94 (git)
Linux	Linux	Affected: 5.12 Unaffected: 0 , < 5.12 (semver) Unaffected: 5.15.196 , ≤ 5.15.* (semver) Unaffected: 6.1.158 , ≤ 6.1.* (semver) Unaffected: 6.6.115 , ≤ 6.6.* (semver) Unaffected: 6.12.56 , ≤ 6.12.* (semver) Unaffected: 6.17.6 , ≤ 6.17.* (semver) Unaffected: 6.18 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/nios2/kernel/setup.c"
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              "status": "unaffected",
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              "versionType": "semver"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnios2: ensure that memblock.current_limit is set when setting pfn limits\n\nOn nios2, with CONFIG_FLATMEM set, the kernel relies on\nmemblock_get_current_limit() to determine the limits of mem_map, in\nparticular for max_low_pfn.\nUnfortunately, memblock.current_limit is only default initialized to\nMEMBLOCK_ALLOC_ANYWHERE at this point of the bootup, potentially leading\nto situations where max_low_pfn can erroneously exceed the value of\nmax_pfn and, thus, the valid range of available DRAM.\n\nThis can in turn cause kernel-level paging failures, e.g.:\n\n[   76.900000] Unable to handle kernel paging request at virtual address 20303000\n[   76.900000] ea = c0080890, ra = c000462c, cause = 14\n[   76.900000] Kernel panic - not syncing: Oops\n[   76.900000] ---[ end Kernel panic - not syncing: Oops ]---\n\nThis patch fixes this by pre-calculating memblock.current_limit\nbased on the upper limits of the available memory ranges via\nadjust_lowmem_bounds, a simplified version of the equivalent\nimplementation within the arm architecture."
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              "value": "AV:L - The defect is in nios2 `setup_arch()` boot-time memory initialization, and its consequences are realized through local activity \u2014 memory allocation and `mmap()`/page-fault paths that call `pfn_valid()`/`pfn_to_page()`. There is no network or remote-peer path to arch/nios2/kernel/setup.c.\nAC:L - `memblock.current_limit` is never set before `find_limits()`, so `max_low_pfn`/`max_mapnr` are unconditionally inflated to ~4 GB of PFNs on every affected nios2 system \u2014 the vulnerable state always exists, with no race and no memory-layout luck required. The attacker only needs to map or touch a physical region above DRAM, which is under their control on these FPGA SoCs where peripheral/on-chip-memory windows sit above RAM.\nPR:L - No capability check guards any of it \u2014 an ordinary unprivileged process reaching `update_mmu_cache_range()`/`flush_dcache_page()` through a fault on a device or PFNMAP mapping, or simply driving allocation into the bogus PFN range, is sufficient. Embedded nios2 deployments routinely expose UIO/framebuffer device nodes to non-root users.\nUI:N - The attacker performs every step themselves \u2014 map the region, touch it, let the fault path run. No action by another user or administrator is needed.\nS:U - The out-of-bounds accesses stay within the kernel\u0027s own memory and security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - `pfn_valid()` wrongly approves PFNs with no memmap entry, so `pfn_to_page()` returns a pointer up to tens of megabytes past the end of `mem_map`, and `folio_flush_mapping()`/`flush_aliases()` read and follow that out-of-bounds kernel data as an `address_space`. This is a wide, PFN-indexed out-of-bounds read, far beyond a strictly bounded few bytes.\nI:H - `update_mmu_cache_range()` performs `test_and_set_bit(PG_dcache_clean, \u0026folio-\u003eflags.f)` on the out-of-bounds `struct page`, an attacker-positioned out-of-bounds atomic write into arbitrary kernel memory, and then walks a garbage `address_space`/i_mmap tree. Per the OOB-write guidance this is High.\nA:H - The documented, reproduced impact is a fatal kernel paging fault and panic (\"Unable to handle kernel paging request ... Kernel panic - not syncing: Oops\"), and the corrupted low-memory limits can equally cause the allocator and DMA logic to operate on non-existent DRAM. The condition is triggerable repeatedly at will."
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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