CVE-2025-39827net: rose: include node references in rose_neigh refcount

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4cce478c3e82a5fc788d72adb2f4c4e983997639
• https://git.kernel.org/stable/c/9c547c8eee9d1cf6e744611d688b9f725cf9a115
• https://git.kernel.org/stable/c/d7563b456ed44151e1a82091d96f60166daea89b
• https://git.kernel.org/stable/c/384210cceb1873a4c8218b27ba0745444436b728
• https://git.kernel.org/stable/c/da9c9c877597170b929a6121a68dcd3dd9a80f45
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
• https://cert-portal.siemens.com/productcert/html/ssa-032379.html
• https://cert-portal.siemens.com/productcert/html/ssa-019113.html
• https://cert-portal.siemens.com/productcert/html/ssa-457936.html