CVE-2022-49554 (GCVE-0-2022-49554)
Vulnerability from cvelistv5
Published
2025-02-26 02:14
Modified
2026-08-05 08:55
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: zsmalloc: fix races between asynchronous zspage free and page migration The asynchronous zspage free worker tries to lock a zspage's entire page list without defending against page migration. Since pages which haven't yet been locked can concurrently migrate off the zspage page list while lock_zspage() churns away, lock_zspage() can suffer from a few different lethal races. It can lock a page which no longer belongs to the zspage and unsafely dereference page_private(), it can unsafely dereference a torn pointer to the next page (since there's a data race), and it can observe a spurious NULL pointer to the next page and thus not lock all of the zspage's pages (since a single page migration will reconstruct the entire page list, and create_page_chain() unconditionally zeroes out each list pointer in the process). Fix the races by using migrate_read_lock() in lock_zspage() to synchronize with page migration.
References
Impacted products
Vendor Product Version
Linux Linux Version: 77ff465799c60294e248000cd22ae8171da3304c
Version: 77ff465799c60294e248000cd22ae8171da3304c
Version: 77ff465799c60294e248000cd22ae8171da3304c
Version: 77ff465799c60294e248000cd22ae8171da3304c
Version: 77ff465799c60294e248000cd22ae8171da3304c
Version: 77ff465799c60294e248000cd22ae8171da3304c
Version: 77ff465799c60294e248000cd22ae8171da3304c
Version: 77ff465799c60294e248000cd22ae8171da3304c
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{
  "containers": {
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          "programFiles": [
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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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\nzsmalloc: fix races between asynchronous zspage free and page migration\n\nThe asynchronous zspage free worker tries to lock a zspage\u0027s entire page\nlist without defending against page migration.  Since pages which haven\u0027t\nyet been locked can concurrently migrate off the zspage page list while\nlock_zspage() churns away, lock_zspage() can suffer from a few different\nlethal races.\n\nIt can lock a page which no longer belongs to the zspage and unsafely\ndereference page_private(), it can unsafely dereference a torn pointer to\nthe next page (since there\u0027s a data race), and it can observe a spurious\nNULL pointer to the next page and thus not lock all of the zspage\u0027s pages\n(since a single page migration will reconstruct the entire page list, and\ncreate_page_chain() unconditionally zeroes out each list pointer in the\nprocess).\n\nFix the races by using migrate_read_lock() in lock_zspage() to synchronize\nwith page migration."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable path is in mm/zsmalloc.c (async_free_zspage \u2192 lock_zspage racing with zs_page_migrate), reached when an unprivileged local process drives zram/zswap alloc/free via swap or compressed-page I/O and concurrent compaction; it is not reachable from the network stack.\nAC:L - A local attacker can drive both sides of the race by allocating/freeing zsmalloc-backed swap objects (zs_free \u2192 deferred free) while inducing compaction/migration of those movable zspages, so success does not depend on conditions outside attacker influence.\nPR:L - On common deployments (e.g. Android with zram swap, or zswap with zsmalloc), any unprivileged local user can trigger zs_malloc/zs_free and memory pressure without capabilities or init-namespace root.\nUI:N - Exploitation requires no victim action beyond the system already using zsmalloc-backed zram/zswap; the attacker triggers the race solely through their own memory and I/O activity.\nS:U - Impact stays within the host kernel\u0027s authority (local memory corruption / privilege escalation); this is not a VM escape, IOMMU bypass, or other cross-boundary break.\nC:H - The race can lock the wrong page and dereference page_private(), follow a torn page-\u003eindex pointer, or free a zspage while unlocked pages remain in use\u2014UAF/memory-corruption primitives that enable arbitrary kernel reads.\nI:H - Incomplete locking of the zspage chain while migration rebuilds it via create_page_chain() allows freeing or resetting pages still under migration, yielding heap corruption exploitable for arbitrary writes and control-flow hijacking.\nA:H - The same races produce NULL/invalid pointer dereferences, use-after-free crashes, and kernel oops/panic when page_private or list links are observed inconsistently during free versus migration."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T08:55:40.785Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/3674d8a8dadd03a447dd21069d4dacfc3399b63b"
        },
        {
          "url": "https://git.kernel.org/stable/c/645996efc2ae391246d595832aaa6f9d3cc338c7"
        },
        {
          "url": "https://git.kernel.org/stable/c/fc658c083904427abbf8f18280d517ee2668677c"
        },
        {
          "url": "https://git.kernel.org/stable/c/fae05b2314b147a78fbed1dc4c645d9a66313758"
        },
        {
          "url": "https://git.kernel.org/stable/c/3ec459c8810e658401be428d3168eacfc380bdd0"
        },
        {
          "url": "https://git.kernel.org/stable/c/8ba7b7c1dad1f6503c541778f31b33f7f62eb966"
        },
        {
          "url": "https://git.kernel.org/stable/c/c5402fb5f71f1a725f1e55d9c6799c0c7bec308f"
        },
        {
          "url": "https://git.kernel.org/stable/c/2505a981114dcb715f8977b8433f7540854851d8"
        }
      ],
      "title": "zsmalloc: fix races between asynchronous zspage free and page migration",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2022-49554",
    "datePublished": "2025-02-26T02:14:02.649Z",
    "dateReserved": "2025-02-26T02:08:31.590Z",
    "dateUpdated": "2026-08-05T08:55:40.785Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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