Medium [CVE-2026-68450] free mapping node on duplicate reloc root insert
This medium-severity Red Hat Linux advisory covers CVE-2026-68450 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4.
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Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: free mapping node on duplicate reloc root insert __add_reloc_root() allocates a mapping_node before inserting it into rc->reloc_root_tree. If rb_simple_insert() finds an existing entry, it returns the existing rb_node and leaves the newly allocated node unlinked.
The error path then returns -EEXIST without freeing the new node. Since the node was never inserted into reloc_root_tree, the later cleanup in put_reloc_control() cannot find it either.
Free the newly allocated node before returning -EEXIST. The callers currently assert that -EEXIST should not happen, so this is a defensive cleanup for an unexpected duplicate insert path.
If the path is ever reached, the local allocation should still be released. When the `__add_reloc_root()` function attempts to insert a duplicate mapping node into the `reloc_root_tree`, the newly allocated node is not properly freed.
This oversight can lead to a memory leak, potentially causing resource exhaustion and a Denial of Service (DoS) over an extended period if this unexpected path is triggered. Red Hat has determined that this vulnerability does not pose a significant risk.
The memory leak occurs on a defensive error path that upstream callers assert should never be reached, and triggering btrfs relocation requires administrative privileges.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
Mitigation checklist
- There is no mitigation for this flaw. Systems not using btrfs filesystems are not affected in practice, as the vulnerable code path is only reached during btrfs block group relocation operations.
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
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