CVE-2025-39941 (GCVE-0-2025-39941)
Vulnerability from cvelistv5
Published
2025-10-04 07:31
Modified
2025-10-04 07:31
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: zram: fix slot write race condition Parallel concurrent writes to the same zram index result in leaked zsmalloc handles. Schematically we can have something like this: CPU0 CPU1 zram_slot_lock() zs_free(handle) zram_slot_lock() zram_slot_lock() zs_free(handle) zram_slot_lock() compress compress handle = zs_malloc() handle = zs_malloc() zram_slot_lock zram_set_handle(handle) zram_slot_lock zram_slot_lock zram_set_handle(handle) zram_slot_lock Either CPU0 or CPU1 zsmalloc handle will leak because zs_free() is done too early. In fact, we need to reset zram entry right before we set its new handle, all under the same slot lock scope.
References
Impacted products
Vendor Product Version
Linux Linux Version: 71268035f5d734ad6373d953298bd5779985497a
Version: 71268035f5d734ad6373d953298bd5779985497a
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{
  "containers": {
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/block/zram/zram_drv.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "versionType": "git"
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          "programFiles": [
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          "vendor": "Linux",
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              "versionType": "semver"
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              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
        {
          "nodes": [
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                  "vulnerable": true
                },
                {
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                  "versionEndExcluding": "6.17",
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nzram: fix slot write race condition\n\nParallel concurrent writes to the same zram index result in leaked\nzsmalloc handles.  Schematically we can have something like this:\n\nCPU0                              CPU1\nzram_slot_lock()\nzs_free(handle)\nzram_slot_lock()\n\t\t\t\tzram_slot_lock()\n\t\t\t\tzs_free(handle)\n\t\t\t\tzram_slot_lock()\n\ncompress\t\t\tcompress\nhandle = zs_malloc()\t\thandle = zs_malloc()\nzram_slot_lock\nzram_set_handle(handle)\nzram_slot_lock\n\t\t\t\tzram_slot_lock\n\t\t\t\tzram_set_handle(handle)\n\t\t\t\tzram_slot_lock\n\nEither CPU0 or CPU1 zsmalloc handle will leak because zs_free() is done\ntoo early.  In fact, we need to reset zram entry right before we set its\nnew handle, all under the same slot lock scope."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-10-04T07:31:04.080Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ff750e9f2c4d63854c33967d1646b5e89a9a19a2"
        },
        {
          "url": "https://git.kernel.org/stable/c/ce4be9e4307c5a60701ff6e0cafa74caffdc54ce"
        }
      ],
      "title": "zram: fix slot write race condition",
      "x_generator": {
        "engine": "bippy-1.2.0"
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    }
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39941",
    "datePublished": "2025-10-04T07:31:04.080Z",
    "dateReserved": "2025-04-16T07:20:57.148Z",
    "dateUpdated": "2025-10-04T07:31:04.080Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-39941\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-10-04T08:15:47.103\",\"lastModified\":\"2025-10-06T14:56:47.823\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nzram: fix slot write race condition\\n\\nParallel concurrent writes to the same zram index result in leaked\\nzsmalloc handles.  Schematically we can have something like this:\\n\\nCPU0                              CPU1\\nzram_slot_lock()\\nzs_free(handle)\\nzram_slot_lock()\\n\\t\\t\\t\\tzram_slot_lock()\\n\\t\\t\\t\\tzs_free(handle)\\n\\t\\t\\t\\tzram_slot_lock()\\n\\ncompress\\t\\t\\tcompress\\nhandle = zs_malloc()\\t\\thandle = zs_malloc()\\nzram_slot_lock\\nzram_set_handle(handle)\\nzram_slot_lock\\n\\t\\t\\t\\tzram_slot_lock\\n\\t\\t\\t\\tzram_set_handle(handle)\\n\\t\\t\\t\\tzram_slot_lock\\n\\nEither CPU0 or CPU1 zsmalloc handle will leak because zs_free() is done\\ntoo early.  In fact, we need to reset zram entry right before we set its\\nnew handle, all under the same slot lock scope.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/ce4be9e4307c5a60701ff6e0cafa74caffdc54ce\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ff750e9f2c4d63854c33967d1646b5e89a9a19a2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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