CVE-2026-89645
Low risk· EPSS 13%Exploitation Probability (EPSS)
Low risk13th percentile - higher than 13% of all known CVEs
Summary
In the Linux kernel, btrfs_recover_relocation() leaks reloc_root references on recovery failure. When loading or adding a later root fails, or the first transaction commit fails, the out_unset path does not drop references held by fs_root->reloc_root, leaving them behind. The fix keeps temporary references to fs roots and drops them on failure.
Risk Assessment
The reference leak can lead to resource exhaustion and btrfs filesystem instability, especially on errors such as -ENOMEM during mount. In extreme cases it may cause denial of service or data integrity issues.
Recommendation
Update the Linux kernel to a version containing this fix. Monitor btrfs systems for mount failures and unexpected memory usage.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: btrfs: drop recovered reloc root refs on recovery failure During relocation recovery, each fs root gets a reference to its relocation root. If loading or adding a later root fails, or if the first transaction commit fails, btrfs_recover_relocation() jumps to out_unset before merge_reloc_roots() and clean_dirty_subvols(). put_reloc_control() drops the list-owned relocation root references, but it does not clear fs_root->reloc_root or drop the references owned by those pointers. Mount cleanup only drops them when BTRFS_FS_ERROR is set, so an error such as -ENOMEM while processing a later root can leave references behind. Keep temporary references to the fs roots associated during recovery. On failure, clear their reloc_root pointers and drop the corresponding references. Once the first transaction commit succeeds, drop only the temporary fs root references and let the normal merge and cleanup paths handle the relocation roots. Fault injection on a pending-relocation image confirmed the cleanup gap. With an injected first-commit failure, 25 fs roots had reloc_root set with fs_error=0. With this fix, the same failure path drops that count to 0 before mount fails.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS