btrfs: fix failure to rebuild free space tree using multiple transactions

{
  "id": "e05d27123ab9e0158ce491b2b46b7bc47bbcfdfdc2c2318a4f9a5a1688dc0732",
  "url": "https://osv.dev/vulnerability/CVE-2025-38370",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "btrfs: fix failure to rebuild free space tree using multiple transactions",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: btrfs: fix failure to rebuild free space tree using multiple transactions If we are rebuilding a free space tree, while modifying the free space tree we may need to allocate a new metadata block group. If we end up using multiple transactions for the rebuild, when we call btrfs_end_transaction() we enter btrfs_create_pending_block_groups() which calls add_block_group_free_space() to add items to the free space tree for the block group. Then later during the free space tree rebuild, at btrfs_rebuild_free_space_tree(), we may find such new block groups and call populate_free_space_tree() for them, which fails with -EEXIST because there are already items in the free space tree. Then we abort the transaction with -EEXIST at btrfs_rebuild_free_space_tree(). Notice that we say \"may find\" the new block groups because a new block group may be inserted in the block groups rbtree, which is being iterated by the rebuild process, before or after the current node where the rebuild process is currently at. Syzbot recently reported such case which produces a trace like the following: ------------[ cut here ]------------ BTRFS: Transaction aborted (error -17) WARNING: CPU: 1 PID: 7626 at fs/btrfs/free-space-tree.c:1341 btrfs_rebuild_free_space_tree+0x470/0x54c fs/btrfs/free-space-tree.c:1341 Modules linked in: CPU: 1 UID: 0 PID: 7626 Comm: syz.2.25 Not tainted 6.15.0-rc7-syzkaller-00085-gd7fa1af5b33e-dirty #0 PREEMPT Hardwar",
    "evidence": "osv:CVE-2025-38370",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.15.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-38370",
      "aliases": [
        "CVE-2025-38370"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "882af9f13e830c0a4ef696bb72cd5998a5067a93"
                },
                {
                  "fixed": "88fdd4899ea9bfe6cf943f099fcf8ad5df153782"
                },
                {
                  "fixed": "1e6ed33cabba8f06f532f2e5851a102602823734"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-38370.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.14.0"
                },
                {
                  "fixed": "6.15.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-38370.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:46.187914656Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1e6ed33cabba8f06f532f2e5851a102602823734",
        "https://git.kernel.org/stable/c/88fdd4899ea9bfe6cf943f099fcf8ad5df153782",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38370.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-38370",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38370.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-38370",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 514027,
  "published_at": "2025-07-25T12:53:13.515+00:00"
}