CVE-2025-39941 (GCVE-0-2025-39941)

Vulnerability from cvelistv5 – Published: 2025-10-04 07:31 – Updated: 2025-10-04 07:31
VLAI?
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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 71268035f5d734ad6373d953298bd5779985497a , < ff750e9f2c4d63854c33967d1646b5e89a9a19a2 (git)
Affected: 71268035f5d734ad6373d953298bd5779985497a , < ce4be9e4307c5a60701ff6e0cafa74caffdc54ce (git)
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    Linux Linux Affected: 6.14
Unaffected: 0 , < 6.14 (semver)
Unaffected: 6.16.9 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
            "drivers/block/zram/zram_drv.c"
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      "descriptions": [
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          "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"
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          "url": "https://git.kernel.org/stable/c/ff750e9f2c4d63854c33967d1646b5e89a9a19a2"
        },
        {
          "url": "https://git.kernel.org/stable/c/ce4be9e4307c5a60701ff6e0cafa74caffdc54ce"
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      ],
      "title": "zram: fix slot write race condition",
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  "cveMetadata": {
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    "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"
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    "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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