CVE-2025-39826

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

net: rose: convert 'use' field to refcount_t

The 'use' field in struct rose_neigh is used as a reference counter but lacks atomicity. This can lead to race conditions where a rose_neigh structure is freed while still being referenced by other code paths.

For example, when rose_neigh->use becomes zero during an ioctl operation via rose_rt_ioctl(), the structure may be removed while its timer is still active, potentially causing use-after-free issues.

This patch changes the type of 'use' from unsigned short to refcount_t and updates all code paths to use rose_neigh_hold() and rose_neigh_put() which operate reference counts atomically.

This vulnerability does not affect Red Hat Enterprise Linux products because the ROSE amateur radio protocol driver (CONFIG_ROSE) is not enabled or shipped in supported Red Hat kernels. The flaw stems from non-atomic reference counter operations in the amateur radio networking subsystem, which could allow a local attacker to cause a race condition and subsequent memory corruption. Because the underlying network module is neither built nor available in standard distributions, Red Hat installations are not exposed to this risk.