In the Linux kernel, the following vulnerability has been resolved:

dm-thin: fix metadata refcount underflow

There's a bug in dm-thin in the function rebalance_children. If the
internal btree node has one entry, the code tries to copy all btree
entries from the node's child to the node itself and then decrement the
child's reference count.

If the child node is shared (it has reference count > 1), we won't free
it, so there would be two pointers to each of the grandchildren nodes.
But the reference counts of the grandchildren is not increased, thus the
reference count doesn't match the number of pointers that point to the
grandchildren. This results in "device mapper: space map common: unable
to decrement block" errors.

Fix this bug by incrementing reference counts on the grandchildren if the
btree node is shared.

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History

Thu, 28 May 2026 11:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-612

Thu, 28 May 2026 10:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: dm-thin: fix metadata refcount underflow There's a bug in dm-thin in the function rebalance_children. If the internal btree node has one entry, the code tries to copy all btree entries from the node's child to the node itself and then decrement the child's reference count. If the child node is shared (it has reference count > 1), we won't free it, so there would be two pointers to each of the grandchildren nodes. But the reference counts of the grandchildren is not increased, thus the reference count doesn't match the number of pointers that point to the grandchildren. This results in "device mapper: space map common: unable to decrement block" errors. Fix this bug by incrementing reference counts on the grandchildren if the btree node is shared.
Title dm-thin: fix metadata refcount underflow
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-05-28T09:35:13.051Z

Reserved: 2026-05-13T15:03:33.098Z

Link: CVE-2026-46107

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-05-28T10:16:26.063

Modified: 2026-05-28T13:44:01.663

Link: CVE-2026-46107

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-28T12:00:12Z

Weaknesses