Overview
About vulnerability
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.
Details
- Affected product:
- Ubuntu 20.04 ELS
- Affected packages:
- linux-meta @ 5.4.0
Fixes
KernelCare state
Live-patch status from KernelCare for each operating system.
| Operating system | Status | Covered kernels |
|---|---|---|
| Amazon Linux 2023 | Planned | — |
| Debian 11 | Planned | — |
| Debian 11 cloud | Planned | — |
| Debian 12 | Planned | — |
| Debian 13 | Planned | — |
| Ubuntu 22.04 | Planned | — |
| Ubuntu 24.04 | Planned | — |