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

Vulnerability from cvelistv5 – Published: 2025-12-04 15:31 – Updated: 2026-08-05 12:08
VLAI
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
References
Impacted products
Vendor Product Version CPE status
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)
guessed Create a notification for this product.
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)
guessed Create a notification for this product.
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          "lang": "en",
          "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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              "lang": "en",
              "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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    "cveId": "CVE-2025-40245",
    "datePublished": "2025-12-04T15:31:34.142Z",
    "dateReserved": "2025-04-16T07:20:57.181Z",
    "dateUpdated": "2026-08-05T12:08:49.485Z",
    "state": "PUBLISHED"
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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.\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"arch/nios2/kernel/setup.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae\",\"lessThan\":\"25f09699edd360b534ccae16bc276c3b52c471f3\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae\",\"lessThan\":\"5c3e38a367822f036227dd52bac82dc4a05157e2\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae\",\"lessThan\":\"b1ec9faef7e36269ca3ec890972a78effbaeb975\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae\",\"lessThan\":\"90f5f715550e07cd6a51f80fc3f062d832c8c997\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae\",\"lessThan\":\"8912814f14e298b83df072fecc1f7ed1b63b1b2c\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"7f7bc20bc41a4fbcd2db75b375ac95e5faf958ae\",\"lessThan\":\"a20b83cf45be2057f3d073506779e52c7fa17f94\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"arch/nios2/kernel/setup.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.12\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.12\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.196\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.158\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.115\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.56\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.17.6\",\"lessThanOrEqual\":\"6.17.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/25f09699edd360b534ccae16bc276c3b52c471f3\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5c3e38a367822f036227dd52bac82dc4a05157e2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8912814f14e298b83df072fecc1f7ed1b63b1b2c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/90f5f715550e07cd6a51f80fc3f062d832c8c997\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a20b83cf45be2057f3d073506779e52c7fa17f94\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b1ec9faef7e36269ca3ec890972a78effbaeb975\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-06-30T10:15:44+00:00",
      "cve": "CVE-2025-40245",
      "id": "CVE-2025-40245",
      "initial_release_date": "2025-12-04T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: nios2: ensure that memblock.current_limit is set when setting pfn limits",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40245.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-28T16:54:39Z",
      "cve": "CVE-2025-40245",
      "id": "CVE-2025-40245",
      "initial_release_date": "2025-12-05T00:25:37Z",
      "product_status:known_not_affected": "560",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-40245",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-40245.json",
      "version": "17"
    }
  }
}



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