{"api_version":"1","generated_at":"2026-07-23T11:17:00+00:00","cve":"CVE-2025-39686","urls":{"html":"https://cve.report/CVE-2025-39686","api":"https://cve.report/api/cve/CVE-2025-39686.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2025-39686","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-39686"},"summary":{"title":"comedi: Make insn_rw_emulate_bits() do insn->n samples","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ncomedi: Make insn_rw_emulate_bits() do insn->n samples\n\nThe `insn_rw_emulate_bits()` function is used as a default handler for\n`INSN_READ` instructions for subdevices that have a handler for\n`INSN_BITS` but not for `INSN_READ`.  Similarly, it is used as a default\nhandler for `INSN_WRITE` instructions for subdevices that have a handler\nfor `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the\n`INSN_READ` or `INSN_WRITE` instruction handling with a constructed\n`INSN_BITS` instruction.  However, `INSN_READ` and `INSN_WRITE`\ninstructions are supposed to be able read or write multiple samples,\nindicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently\nonly handles a single sample.  For `INSN_READ`, the comedi core will\ncopy `insn->n` samples back to user-space.  (That triggered KASAN\nkernel-infoleak errors when `insn->n` was greater than 1, but that is\nbeing fixed more generally elsewhere in the comedi core.)\n\nMake `insn_rw_emulate_bits()` either handle `insn->n` samples, or return\nan error, to conform to the general expectation for `INSN_READ` and\n`INSN_WRITE` handlers.","state":"PUBLISHED","assigner":"Linux","published_at":"2025-09-05 18:15:45","updated_at":"2026-05-12 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the Linux kernel, the following vulnerability has been resolved:\n\ncomedi: Make insn_rw_emulate_bits() do insn->n samples\n\nThe `insn_rw_emulate_bits()` function is used as a default handler for\n`INSN_READ` instructions for subdevices that have a handler for\n`INSN_BITS` but not for `INSN_READ`.  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Similarly, it is used as a default\nhandler for `INSN_WRITE` instructions for subdevices that have a handler\nfor `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the\n`INSN_READ` or `INSN_WRITE` instruction handling with a constructed\n`INSN_BITS` instruction.  However, `INSN_READ` and `INSN_WRITE`\ninstructions are supposed to be able read or write multiple samples,\nindicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently\nonly handles a single sample.  For `INSN_READ`, the comedi core will\ncopy `insn->n` samples back to user-space.  (That triggered KASAN\nkernel-infoleak errors when `insn->n` was greater than 1, but that is\nbeing fixed more generally elsewhere in the comedi core.)\n\nMake `insn_rw_emulate_bits()` either handle `insn->n` samples, or return\nan error, to conform to the general expectation for `INSN_READ` and\n`INSN_WRITE` handlers.","Type":"Description","Title":"comedi: Make insn_rw_emulate_bits() do insn->n samples"}]}}}