CVE-2026-98254 (GCVE-0-2026-98254)
Vulnerability from cvelistv5
Published
2026-10-06 08:45
Modified
2026-10-19 09:16
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: swiotlb: use the adjusted address for the highmem page lookup swiotlb_bounce() reads the page frame number from the slot's recorded orig_addr, then advances orig_addr by tlb_offset to reach the address the caller asked about. The highmem branch mixes the two: the offset within the page comes from the adjusted address, the page from the value before it. Once the adjustment crosses a page boundary the pair no longer describes one location, and the whole copy lands one page below the intended one for a positive tlb_offset, one above for a negative one. DMA_FROM_DEVICE writes the device data over the wrong page and leaves the intended one stale, DMA_TO_DEVICE feeds the device from a page the mapping may not cover. Partial syncs through dma_sync_single_range_for_*() are what make tlb_offset non-zero. The branch test is picked the same way, so a slot recorded in lowmem can be adjusted into highmem and the lowmem path then hands a highmem address to phys_to_virt(). Take both from orig_addr once it is final and keep pfn in the branch that uses it. PhysHighMem() asks the question straight from the address, as dma-debug already does.
References
Impacted products
Vendor Product Version
Linux Linux Version: 5f89468e2f060031cd89fd4287298e0eaf246bf6
Version: 5f89468e2f060031cd89fd4287298e0eaf246bf6
Version: 5f89468e2f060031cd89fd4287298e0eaf246bf6
Version: 5f89468e2f060031cd89fd4287298e0eaf246bf6
Version: e6108147dd91b94d1979b110f265710c254c99d5
Version: e77b796eb9b7ca3c1c0d574d0c155f55b59ca8d5
Version: 5.10.47   ≤
Version: 5.12.14   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/dma/swiotlb.c"
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          "programFiles": [
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              "version": "7.2.8",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
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                  "versionEndExcluding": "6.12.112",
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                  "vulnerable": true
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              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nswiotlb: use the adjusted address for the highmem page lookup\n\nswiotlb_bounce() reads the page frame number from the slot\u0027s recorded\norig_addr, then advances orig_addr by tlb_offset to reach the address\nthe caller asked about. The highmem branch mixes the two: the offset\nwithin the page comes from the adjusted address, the page from the value\nbefore it.\n\nOnce the adjustment crosses a page boundary the pair no longer describes\none location, and the whole copy lands one page below the intended one\nfor a positive tlb_offset, one above for a negative one. DMA_FROM_DEVICE\nwrites the device data over the wrong page and leaves the intended one\nstale, DMA_TO_DEVICE feeds the device from a page the mapping may not\ncover. Partial syncs through dma_sync_single_range_for_*() are what make\ntlb_offset non-zero.\n\nThe branch test is picked the same way, so a slot recorded in lowmem can\nbe adjusted into highmem and the lowmem path then hands a highmem\naddress to phys_to_virt().\n\nTake both from orig_addr once it is final and keep pfn in the branch\nthat uses it. PhysHighMem() asks the question straight from the address,\nas dma-debug already does."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The defect is in swiotlb_bounce(), reached only via __swiotlb_sync_single_for_cpu/_for_device from a driver\u0027s dma_sync_single_range_for_*() on a bounced buffer. No protocol message carries malformed input, and a local user can only cause it by doing I/O on a highmem buffer through such a driver.\nAC:L - Not used; the AC line below is the real value.\nPR:L - The attacker needs an ordinary local account to issue I/O whose buffers (user or page-cache pages, which can be highmem) go through an affected device\u0027s streaming DMA mapping. No capability check on the swiotlb sync path stands in the way.\nUI:N - Once the attacker\u0027s own I/O drives the partial-sync pattern, no victim action is needed. The bounce runs inside the driver\u0027s sync call.\nS:U - The bad copy is done by the kernel\u0027s own swiotlb code into kernel-managed physical memory. No IOMMU, VM or other boundary is crossed beyond the kernel\u0027s own authority.\nC:H - On DMA_TO_DEVICE, memcpy_from_page() uses pfn_to_page(PFN_DOWN(old orig_addr)) and feeds the device a whole neighbouring physical page the mapping does not cover. This can expose unrelated kernel or user data to the device.\nI:H - On DMA_FROM_DEVICE, memcpy_to_page() writes device data over the page next to the intended one, corrupting arbitrary neighbouring memory. Separately, a lowmem slot shifted into highmem sends a highmem address to phys_to_virt() and memcpy() through a bogus pointer.\nA:H - Overwriting an unrelated physical page, or calling memcpy() on a bogus phys_to_virt() pointer for a highmem address, can corrupt kernel state or fault and oops the kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:16:25.551Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/6e53b4d6afbde626255805d438cabb1cac482445"
        },
        {
          "url": "https://git.kernel.org/stable/c/aa4709813b29db89f2307f968db5d24925dcdeb1"
        },
        {
          "url": "https://git.kernel.org/stable/c/0219b72f5c209732b2f03a8cc0d7240b5e428a99"
        },
        {
          "url": "https://git.kernel.org/stable/c/b7d7914a9ae3097e63d113007e4fb44d33d515b1"
        }
      ],
      "title": "swiotlb: use the adjusted address for the highmem page lookup",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98254",
    "datePublished": "2026-10-06T08:45:20.736Z",
    "dateReserved": "2026-09-25T10:25:14.331Z",
    "dateUpdated": "2026-10-19T09:16:25.551Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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