CVE-2026-31516xfrm: prevent policy_hthresh.work from racing with netns teardown

Official description

In the Linux kernel, the following vulnerability has been resolved: xfrm: prevent policy_hthresh.work from racing with netns teardown A XFRM_MSG_NEWSPDINFO request can queue the per-net work item policy_hthresh.work onto the system workqueue. The queued callback, xfrm_hash_rebuild(), retrieves the enclosing struct net via container_of(). If the net namespace is torn down before that work runs, the associated struct net may already have been freed, and xfrm_hash_rebuild() may then dereference stale memory. xfrm_policy_fini() already flushes policy_hash_work during teardown, but it does not synchronize policy_hthresh.work. Synchronize policy_hthresh.work in xfrm_policy_fini() as well, so the queued work cannot outlive the net namespace teardown and access a freed struct net.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/56ea2257b83ee29a543f158159e3d1abc1e3e4fe
• https://git.kernel.org/stable/c/8854e9367465d784046362698731c1111e3b39b8
• https://git.kernel.org/stable/c/4e2e77843fef473ef47e322d52436d8308582a96
• https://git.kernel.org/stable/c/29fe3a61bcdce398ee3955101c39f89c01a8a77e