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.