GHSA-PPP2-86MR-9VH3
Vulnerability from github – Published: 2025-05-09 09:33 – Updated: 2026-10-30 15:32In 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.
{
"affected": [],
"aliases": [
"CVE-2025-37856"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-05-09T07:16:06Z",
"severity": "MODERATE"
},
"details": "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.",
"id": "GHSA-ppp2-86mr-9vh3",
"modified": "2026-10-30T15:32:07Z",
"published": "2025-05-09T09:33:19Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-37856"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/185fd73e5ac06027c4be9a129e59193f6a3ef202"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7511e29cf1355b2c47d0effb39e463119913e2f6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9039afe6240ae01d6caf2fa731590ac74fb8a69b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/909e60fb469d4101c6b08cf6e622efb062bb24a1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bf089c4d1141b27332c092b1dcca5022c415a3b6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ccb20413e7c82e4429c81f10d0e36cd9c0c643cd"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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