CVE-2025-37856btrfs: harden block_group::bg_list against list_del() races
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 21, 2026
- First seen by InfoSec Signals
- Oct 21, 2026
Affected products
Linux Linux linux:linux (from the name) | from a9f189716cf15913c453299d72f69c51a9b0f86b before 9039afe6240ae01d6caf2fa731590ac74fb8a69b; from a9f189716cf15913c453299d72f69c51a9b0f86b before bf089c4d1141b27332c092b1dcca5022c415a3b6; from a9f189716cf15913c453299d72f69c51a9b0f86b before 909e60fb469d4101c6b08cf6e622efb062bb24a1; from a9f189716cf15913c453299d72f69c51a9b0f86b before 185fd73e5ac06027c4be9a129e59193f6a3ef202; from a9f189716cf15913c453299d72f69c51a9b0f86b before 7511e29cf1355b2c47d0effb39e463119913e2f6; edf3b5aadb2515c808200b904baa5b70a727f0ac; 01eca70ef8cf499d0cb6d1bbd691558e7792cf17; 5d19abcffd8404078dfa7d7118cec357b5e7bc58; and 3 more ranges | CNA record |
linux linux_kernel linux:linux_kernel | before 6.12.24; from 6.13 before 6.13.12; from 6.14 before 6.14.3 | NVD |
References
- https://git.kernel.org/stable/c/9039afe6240ae01d6caf2fa731590ac74fb8a69b
- https://git.kernel.org/stable/c/bf089c4d1141b27332c092b1dcca5022c415a3b6patch
- https://git.kernel.org/stable/c/909e60fb469d4101c6b08cf6e622efb062bb24a1patch
- https://git.kernel.org/stable/c/185fd73e5ac06027c4be9a129e59193f6a3ef202patch
- https://git.kernel.org/stable/c/7511e29cf1355b2c47d0effb39e463119913e2f6patch
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.