FKIE_CVE-2026-98116

Vulnerability from fkie_nvd - Published: 2026-09-25 11:17 - Updated: 2026-09-25 15:18
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: ALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF snd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation with an mmap_count check performed under the PCM stream lock, but the lock is released long before the buffer is actually freed: snd_pcm_sync_stop(), constraint refinement and do_free_pages() all happen in between. snd_pcm_mmap_data(), on the other hand, takes no lock at all: it validates against the old buffer's state and dma_bytes, remaps its pages into the VMA, and only then increments mmap_count. A concurrent mmap() can therefore slip in between the check and the free. remap_pfn_range() installs writable PTEs for the old buffer's pages without taking page references, and the subsequent do_free_pages() returns those pages to the page allocator while the VMA still maps them. This leaves a stale, writable mapping of freed pages: a page-level use-after-free that can be leveraged for local privilege escalation. Make snd_pcm_mmap_data() participate in the buffer-access scheme introduced for hw_params/hw_free: acquire runtime->buffer_accessing before validating and remapping, and release it afterwards. Buffer reallocation already fails with -EBUSY while accessors are active, and the mmap side now fails with -EBUSY while a reallocation is in progress, so the validate/remap sequence and the check/free sequence can no longer interleave. A reproducer that turns this race into a stale writable mapping of the freed DMA buffer pages is available on request.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8c1882dfee8f404d118020664b73eb4592172226
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9b110a9dcecc59516c77cb3c0caf1f492f75df2d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fd137bf8149bc6460f9b7b1fc292025da04cb9ee
Impacted products
Vendor Product Version
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{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "sound/core/pcm_native.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5",
              "status": "affected",
              "version": "92ee3c60ec9fe64404dc035e7c41277d74aa26cb",
              "versionType": "git"
            },
            {
              "lessThan": "fd137bf8149bc6460f9b7b1fc292025da04cb9ee",
              "status": "affected",
              "version": "92ee3c60ec9fe64404dc035e7c41277d74aa26cb",
              "versionType": "git"
            },
            {
              "lessThan": "8c1882dfee8f404d118020664b73eb4592172226",
              "status": "affected",
              "version": "92ee3c60ec9fe64404dc035e7c41277d74aa26cb",
              "versionType": "git"
            },
            {
              "lessThan": "9b110a9dcecc59516c77cb3c0caf1f492f75df2d",
              "status": "affected",
              "version": "92ee3c60ec9fe64404dc035e7c41277d74aa26cb",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "a42aa926843acca96c0dfbde2e835b8137f2f092",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "9cb6c40a6ebe4a0cfc9d6a181958211682cffea9",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "fbeb492694ce0441053de57699e1e2b7bc148a69",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0f6947f5f5208f6ebd4d76a82a4757e2839a23f8",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "33061d0fba51d2bf70a2ef9645f703c33fe8e438",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "0090c13cbbdffd7da079ac56f80373a9a1be0bf8",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "1bbf82d9f961414d6c76a08f7f843ea068e0ab7b",
              "versionType": "git"
            },
            {
              "lessThan": "4.15",
              "status": "affected",
              "version": "4.14.279",
              "versionType": "semver"
            },
            {
              "lessThan": "4.20",
              "status": "affected",
              "version": "4.19.243",
              "versionType": "semver"
            },
            {
              "lessThan": "5.5",
              "status": "affected",
              "version": "5.4.193",
              "versionType": "semver"
            },
            {
              "lessThan": "5.11",
              "status": "affected",
              "version": "5.10.109",
              "versionType": "semver"
            },
            {
              "lessThan": "5.16",
              "status": "affected",
              "version": "5.15.32",
              "versionType": "semver"
            },
            {
              "lessThan": "5.17",
              "status": "affected",
              "version": "5.16.18",
              "versionType": "semver"
            },
            {
              "lessThan": "5.18",
              "status": "affected",
              "version": "5.17.1",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "sound/core/pcm_native.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.18"
            },
            {
              "lessThan": "5.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.111",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.53",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.7",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3-rc2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: pcm: Serialize PCM mmap with buffer reallocation to fix page UAF\n\nsnd_pcm_hw_params() and snd_pcm_hw_free() guard buffer reallocation\nwith an mmap_count check performed under the PCM stream lock, but the\nlock is released long before the buffer is actually freed:\nsnd_pcm_sync_stop(), constraint refinement and do_free_pages() all\nhappen in between.  snd_pcm_mmap_data(), on the other hand, takes no\nlock at all: it validates against the old buffer\u0027s state and\ndma_bytes, remaps its pages into the VMA, and only then increments\nmmap_count.\n\nA concurrent mmap() can therefore slip in between the check and the\nfree.  remap_pfn_range() installs writable PTEs for the old buffer\u0027s\npages without taking page references, and the subsequent\ndo_free_pages() returns those pages to the page allocator while the\nVMA still maps them.  This leaves a stale, writable mapping of freed\npages: a page-level use-after-free that can be leveraged for local\nprivilege escalation.\n\nMake snd_pcm_mmap_data() participate in the buffer-access scheme\nintroduced for hw_params/hw_free: acquire runtime-\u003ebuffer_accessing\nbefore validating and remapping, and release it afterwards.  Buffer\nreallocation already fails with -EBUSY while accessors are active,\nand the mmap side now fails with -EBUSY while a reallocation is in\nprogress, so the validate/remap sequence and the check/free sequence\ncan no longer interleave.\n\nA reproducer that turns this race into a stale writable mapping of\nthe freed DMA buffer pages is available on request."
    }
  ],
  "id": "CVE-2026-98116",
  "lastModified": "2026-09-25T15:18:06.437",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-25T11:17:42.780",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/8c1882dfee8f404d118020664b73eb4592172226"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/9b110a9dcecc59516c77cb3c0caf1f492f75df2d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/cbc7ec97601d09b74e05e44470fa6b0bcdabf3f5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/fd137bf8149bc6460f9b7b1fc292025da04cb9ee"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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