CVE-2026-89645
btrfs: drop recovered reloc root refs on recovery failure
Description
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.
INFO
Published Date :
Sept. 11, 2026, 8:19 p.m.
Last Modified :
Sept. 11, 2026, 8:19 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Update the Linux kernel to the latest version.
- Apply the specific patch for the btrfs relocation bug.
- Ensure proper cleanup of relocation roots on failure.
- Verify reference counts after recovery operations.
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CWE - Common Weakness Enumeration
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specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-89645 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
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stores attack patterns, which are descriptions of the common attributes and
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weaknesses.
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Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 11, 2026
Action Type Old Value New Value Added Description 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. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/89xxx/CVE-2026-89645.json">CVE-2026-89645</a> Added Reference https://git.kernel.org/stable/c/2256d6dc5b88841a8a8b4fd9a9f04730705fb6fd Added Reference https://git.kernel.org/stable/c/4d43107e807bcd92621106b07f5011411c6341a8 Added Reference https://git.kernel.org/stable/c/6d8ba4572922e336f0b59a80751b018e1e135164 Added Reference https://git.kernel.org/stable/c/8a64baeb5bbb706b83d2235c1e39f5b77183817f