CVE-2025-38627 (GCVE-0-2025-38627)
Vulnerability from cvelistv5
Published
2025-08-22 16:00
Modified
2026-08-05 12:03
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: f2fs: compress: fix UAF of f2fs_inode_info in f2fs_free_dic The decompress_io_ctx may be released asynchronously after I/O completion. If this file is deleted immediately after read, and the kworker of processing post_read_wq has not been executed yet due to high workloads, It is possible that the inode(f2fs_inode_info) is evicted and freed before it is used f2fs_free_dic. The UAF case as below: Thread A Thread B - f2fs_decompress_end_io - f2fs_put_dic - queue_work add free_dic work to post_read_wq - do_unlink - iput - evict - call_rcu This file is deleted after read. Thread C kworker to process post_read_wq - rcu_do_batch - f2fs_free_inode - kmem_cache_free inode is freed by rcu - process_scheduled_works - f2fs_late_free_dic - f2fs_free_dic - f2fs_release_decomp_mem read (dic->inode)->i_compress_algorithm This patch store compress_algorithm and sbi in dic to avoid inode UAF. In addition, the previous solution is deprecated in [1] may cause system hang. [1] https://lore.kernel.org/all/c36ab955-c8db-4a8b-a9d0-f07b5f426c3f@kernel.org
References
Impacted products
Vendor Product Version
Linux Linux Version: bff139b49d9f70c1ac5384aac94554846aa834de
Version: bff139b49d9f70c1ac5384aac94554846aa834de
Version: bff139b49d9f70c1ac5384aac94554846aa834de
Version: bff139b49d9f70c1ac5384aac94554846aa834de
Version: bff139b49d9f70c1ac5384aac94554846aa834de
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/f2fs/compress.c",
            "fs/f2fs/f2fs.h"
          ],
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        {
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          "product": "Linux",
          "programFiles": [
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            "fs/f2fs/f2fs.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "6.0"
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              "version": "0",
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              "status": "unaffected",
              "version": "6.1.175",
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            },
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              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.118",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.78",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.16.*",
              "status": "unaffected",
              "version": "6.16.1",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.175",
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                  "vulnerable": true
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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\nf2fs: compress: fix UAF of f2fs_inode_info in f2fs_free_dic\n\nThe decompress_io_ctx may be released asynchronously after\nI/O completion. If this file is deleted immediately after read,\nand the kworker of processing post_read_wq has not been executed yet\ndue to high workloads, It is possible that the inode(f2fs_inode_info)\nis evicted and freed before it is used f2fs_free_dic.\n\n    The UAF case as below:\n    Thread A                                      Thread B\n    - f2fs_decompress_end_io\n     - f2fs_put_dic\n      - queue_work\n        add free_dic work to post_read_wq\n                                                   - do_unlink\n                                                    - iput\n                                                     - evict\n                                                      - call_rcu\n    This file is deleted after read.\n\n    Thread C                                 kworker to process post_read_wq\n    - rcu_do_batch\n     - f2fs_free_inode\n      - kmem_cache_free\n     inode is freed by rcu\n                                             - process_scheduled_works\n                                              - f2fs_late_free_dic\n                                               - f2fs_free_dic\n                                                - f2fs_release_decomp_mem\n                                      read (dic-\u003einode)-\u003ei_compress_algorithm\n\nThis patch store compress_algorithm and sbi in dic to avoid inode UAF.\n\nIn addition, the previous solution is deprecated in [1] may cause system hang.\n[1] https://lore.kernel.org/all/c36ab955-c8db-4a8b-a9d0-f07b5f426c3f@kernel.org"
        }
      ],
      "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 whole sequence \u2014 creating a compressed file via `FS_IOC_SETFLAGS`/`compress_extension`, evicting its page cache with `posix_fadvise()`, reading it, and unlinking it \u2014 is performed through ordinary local syscalls on a mounted f2fs volume. No network protocol, remote peer, or adjacent-network data reaches `f2fs_free_dic()`.\nAC:L - The attacker drives both sides of the race: they submit the compressed read that queues `free_work` and they issue the `close()`/`unlink()` that evicts the inode, and they widen the window at will by saturating `post_read_wq` (bounded `max_active = num_online_cpus()`) with concurrent post-read work so the kworker is delayed past the RCU grace period. Every attempt is free and retryable in a loop, and f2fs compression is a mainstream shipping configuration on Android and embedded devices, not a rare option.\nPR:L - No capability, LSM, or namespace gate exists on the path \u2014 `vfs_fileattr_set()` only requires `inode_owner_or_capable()` on the attacker\u0027s own file, and reading/unlinking a file the attacker created needs nothing beyond normal write access to their own directory. An ordinary user account or an Android app with storage access on a compression-enabled f2fs mount suffices.\nUI:N - The attacking process performs every step itself \u2014 create the compressed file, drop its cache, read it, and delete it. No victim must mount a filesystem, open a file, or take any other action.\nS:U - The freed `f2fs_inode_info`, the wild `sbi`/`cops` dereferences, and any resulting corruption all occur within the same kernel\u0027s security authority. No hypervisor, IOMMU, guest, or sandbox boundary is crossed.\nC:H - This is a use-after-free read of a `f2fs_inode_cachep` object whose memory the attacker can groom by spraying after the RCU free, so the values pulled out (`inode-\u003ei_sb`, `i_compress_algorithm`) are attacker-influenced; the tainted `i_compress_algorithm` byte then indexes the 4-entry `f2fs_cops[]` array up to 255 entries out of bounds, reading arbitrary adjacent kernel data. Combined with the wild `sbi` deref, the flaw yields a kernel-memory read primitive usable for KASLR defeat and data disclosure.\nI:H - The garbage `cops` obtained from the out-of-bounds `f2fs_cops[]` index is immediately used for the indirect call `cops-\u003edestroy_decompress_ctx(dic)`, a control-flow hijack primitive, and the wild `sbi` is passed to `page_array_free()` which performs `kmem_cache_free(sbi-\u003epage_array_slab, pages)` \u2014 freeing a live object into an attacker-influenced cache pointer, a classic path to arbitrary heap corruption and privilege escalation. Per UAF scoring, heap grooming of the recycled inode slab gives write as well as read primitives.\nA:H - Even unexploited, dereferencing the freed inode\u0027s `i_sb` and calling through an out-of-bounds `f2fs_cops[]` entry oopses or panics the kernel, and it happens inside a `post_read_wq` kworker so the crash wedges the filesystem\u0027s decompression workqueue rather than just one task. The unprivileged attacker can retry the trigger indefinitely, and `panic_on_oops=1` builds (Android, automotive, embedded) take an immediate full system panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:03:36.334Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/74cbeeca4f16823ba58c882e1d8b836c0e39c93d"
        },
        {
          "url": "https://git.kernel.org/stable/c/5d604d40cd3232b09cb339941ef958e49283ed0a"
        },
        {
          "url": "https://git.kernel.org/stable/c/cc81768212cdc509e5a986274db7bc24d18cde19"
        },
        {
          "url": "https://git.kernel.org/stable/c/8fae5b6addd5f6895e03797b56e3c7b9f9cd15c9"
        },
        {
          "url": "https://git.kernel.org/stable/c/39868685c2a94a70762bc6d77dc81d781d05bff5"
        }
      ],
      "title": "f2fs: compress: fix UAF of f2fs_inode_info in f2fs_free_dic",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-38627",
    "datePublished": "2025-08-22T16:00:35.856Z",
    "dateReserved": "2025-04-16T04:51:24.029Z",
    "dateUpdated": "2026-08-05T12:03:36.334Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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