CVE-2026-46130 (GCVE-0-2026-46130)
Vulnerability from cvelistv5
Published
2026-05-28 09:35
Modified
2026-08-03 09:32
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: dm-verity-fec: fix reading parity bytes split across blocks (take 3) fec_decode_bufs() assumes that the parity bytes of the first RS codeword it decodes are never split across parity blocks. This assumption is false. Consider v->fec->block_size == 4096 && v->fec->roots == 17 && fio->nbufs == 1, for example. In that case, each call to fec_decode_bufs() consumes v->fec->roots * (fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS) = 272 parity bytes. Considering that the parity data for each message block starts on a block boundary, the byte alignment in the parity data will iterate through 272*i mod 4096 until the 3 parity blocks have been consumed. On the 16th call (i=15), the alignment will be 4080 bytes into the first block. Only 16 bytes remain in that block, but 17 parity bytes will be needed. The code reads out-of-bounds from the parity block buffer. Fortunately this doesn't normally happen, since it can occur only for certain non-default values of fec_roots *and* when the maximum number of buffers couldn't be allocated due to low memory. For example with block_size=4096 only the following cases are affected: fec_roots=17: nbufs in [1, 3, 5, 15] fec_roots=19: nbufs in [1, 229] fec_roots=21: nbufs in [1, 3, 5, 13, 15, 39, 65, 195] fec_roots=23: nbufs in [1, 89] Regardless, fix it by refactoring how the parity blocks are read.
References
Impacted products
Vendor Product Version
Linux Linux Version: 6df90c02bae468a3a6110bafbc659884d0c4966c
Version: 6df90c02bae468a3a6110bafbc659884d0c4966c
Version: 6df90c02bae468a3a6110bafbc659884d0c4966c
Version: 6bc6ee31113b05db605694491bdeb2b1730142f1
Version: 12caa73a28f0ae147ec0356b45091edf2462462b
Version: fc8943886629e26de34867db302c74d465510826
Version: 6.1.125   ≤
Version: 6.6.72   ≤
Version: 6.12.10   ≤
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ndm-verity-fec: fix reading parity bytes split across blocks (take 3)\n\nfec_decode_bufs() assumes that the parity bytes of the first RS codeword\nit decodes are never split across parity blocks.\n\nThis assumption is false.  Consider v-\u003efec-\u003eblock_size == 4096 \u0026\u0026\nv-\u003efec-\u003eroots == 17 \u0026\u0026 fio-\u003enbufs == 1, for example.  In that case, each\ncall to fec_decode_bufs() consumes v-\u003efec-\u003eroots * (fio-\u003enbufs \u003c\u003c\nDM_VERITY_FEC_BUF_RS_BITS) = 272 parity bytes.\n\nConsidering that the parity data for each message block starts on a\nblock boundary, the byte alignment in the parity data will iterate\nthrough 272*i mod 4096 until the 3 parity blocks have been consumed.  On\nthe 16th call (i=15), the alignment will be 4080 bytes into the first\nblock.  Only 16 bytes remain in that block, but 17 parity bytes will be\nneeded.  The code reads out-of-bounds from the parity block buffer.\n\nFortunately this doesn\u0027t normally happen, since it can occur only for\ncertain non-default values of fec_roots *and* when the maximum number of\nbuffers couldn\u0027t be allocated due to low memory.  For example with\nblock_size=4096 only the following cases are affected:\n\n    fec_roots=17: nbufs in [1, 3, 5, 15]\n    fec_roots=19: nbufs in [1, 229]\n    fec_roots=21: nbufs in [1, 3, 5, 13, 15, 39, 65, 195]\n    fec_roots=23: nbufs in [1, 89]\n\nRegardless, fix it by refactoring how the parity blocks are read."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-03T09:32:32.606Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/d47281b9a4472cfd73122393e79fbe76b651e46a"
        },
        {
          "url": "https://git.kernel.org/stable/c/3d1b4e2d8ac0a1a1390a117f61ce0ca1c47e3bcb"
        },
        {
          "url": "https://git.kernel.org/stable/c/430a05cb926f6bdf53e81460a2c3a553257f3f61"
        }
      ],
      "title": "dm-verity-fec: fix reading parity bytes split across blocks (take 3)",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-46130",
    "datePublished": "2026-05-28T09:35:45.387Z",
    "dateReserved": "2026-05-13T15:03:33.099Z",
    "dateUpdated": "2026-08-03T09:32:32.606Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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