CVE-2025-39827

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

net: rose: include node references in rose_neigh refcount

Current implementation maintains two separate reference counting mechanisms: the 'count' field in struct rose_neigh tracks references from rose_node structures, while the 'use' field (now refcount_t) tracks references from rose_sock.

This patch merges these two reference counting systems using 'use' field for proper reference management. Specifically, this patch adds incrementing and decrementing of rose_neigh->use when rose_neigh->count is incremented or decremented.

This patch also modifies rose_rt_free(), rose_rt_device_down() and rose_clear_route() to properly release references to rose_neigh objects before freeing a rose_node through rose_remove_node().

These changes ensure rose_neigh structures are properly freed only when all references, including those from rose_node structures, are released. As a result, this resolves a slab-use-after-free issue reported by Syzbot.

This vulnerability does not affect Red Hat Enterprise Linux or other supported products because the amateur radio ROSE networking protocol is not enabled in Red Hat kernel builds. The underlying subsystem code is omitted during compilation, precluding exposure to the use-after-free flaw on standard installations. As a result, supported Red Hat systems are not vulnerable to this issue.