CVE-2025-37856 (GCVE-0-2025-37856)

Vulnerability from cvelistv5 – Published: 2025-05-09 06:42 – Updated: 2026-01-02 15:29
VLAI?
Title
btrfs: harden block_group::bg_list against list_del() races
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: harden block_group::bg_list against list_del() races As far as I can tell, these calls of list_del_init() on bg_list cannot run concurrently with btrfs_mark_bg_unused() or btrfs_mark_bg_to_reclaim(), as they are in transaction error paths and situations where the block group is readonly. However, if there is any chance at all of racing with mark_bg_unused(), or a different future user of bg_list, better to be safe than sorry. Otherwise we risk the following interleaving (bg_list refcount in parens) T1 (some random op) T2 (btrfs_mark_bg_unused) !list_empty(&bg->bg_list); (1) list_del_init(&bg->bg_list); (1) list_move_tail (1) btrfs_put_block_group (0) btrfs_delete_unused_bgs bg = list_first_entry list_del_init(&bg->bg_list); btrfs_put_block_group(bg); (-1) Ultimately, this results in a broken ref count that hits zero one deref early and the real final deref underflows the refcount, resulting in a WARNING.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: a9f189716cf15913c453299d72f69c51a9b0f86b , < bf089c4d1141b27332c092b1dcca5022c415a3b6 (git)
Affected: a9f189716cf15913c453299d72f69c51a9b0f86b , < 909e60fb469d4101c6b08cf6e622efb062bb24a1 (git)
Affected: a9f189716cf15913c453299d72f69c51a9b0f86b , < 185fd73e5ac06027c4be9a129e59193f6a3ef202 (git)
Affected: a9f189716cf15913c453299d72f69c51a9b0f86b , < 7511e29cf1355b2c47d0effb39e463119913e2f6 (git)
Affected: edf3b5aadb2515c808200b904baa5b70a727f0ac (git)
Affected: 01eca70ef8cf499d0cb6d1bbd691558e7792cf17 (git)
Affected: 5d19abcffd8404078dfa7d7118cec357b5e7bc58 (git)
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    Linux Linux Affected: 6.5
Unaffected: 0 , < 6.5 (semver)
Unaffected: 6.12.24 , ≤ 6.12.* (semver)
Unaffected: 6.13.12 , ≤ 6.13.* (semver)
Unaffected: 6.14.3 , ≤ 6.14.* (semver)
Unaffected: 6.15 , ≤ * (original_commit_for_fix)
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: harden block_group::bg_list against list_del() races\n\nAs far as I can tell, these calls of list_del_init() on bg_list cannot\nrun concurrently with btrfs_mark_bg_unused() or btrfs_mark_bg_to_reclaim(),\nas they are in transaction error paths and situations where the block\ngroup is readonly.\n\nHowever, if there is any chance at all of racing with mark_bg_unused(),\nor a different future user of bg_list, better to be safe than sorry.\n\nOtherwise we risk the following interleaving (bg_list refcount in parens)\n\nT1 (some random op)                       T2 (btrfs_mark_bg_unused)\n                                        !list_empty(\u0026bg-\u003ebg_list); (1)\nlist_del_init(\u0026bg-\u003ebg_list); (1)\n                                        list_move_tail (1)\nbtrfs_put_block_group (0)\n                                        btrfs_delete_unused_bgs\n                                             bg = list_first_entry\n                                             list_del_init(\u0026bg-\u003ebg_list);\n                                             btrfs_put_block_group(bg); (-1)\n\nUltimately, this results in a broken ref count that hits zero one deref\nearly and the real final deref underflows the refcount, resulting in a WARNING."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-01-02T15:29:17.695Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/bf089c4d1141b27332c092b1dcca5022c415a3b6"
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          "url": "https://git.kernel.org/stable/c/909e60fb469d4101c6b08cf6e622efb062bb24a1"
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        },
        {
          "url": "https://git.kernel.org/stable/c/7511e29cf1355b2c47d0effb39e463119913e2f6"
        }
      ],
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-37856",
    "datePublished": "2025-05-09T06:42:04.315Z",
    "dateReserved": "2025-04-16T04:51:23.956Z",
    "dateUpdated": "2026-01-02T15:29:17.695Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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