CVE-2026-97971

/// Technical description

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

nstree: check listing permission before taking a namespace reference

legitimize_ns() takes a reference on the candidate namespace before

may_list_ns() has decided whether the caller may see it. The

__free(ns_put) cleanup on the denied path can drop the last reference to a

mount namespace while we still hold the rcu read lock, and put_mnt_ns()

may sleep there. This is the same problem commit 2ec2aff3c8e2 ("ns: make

sure reference are dropped outside of rcu lock") fixed for the put_user()

path. Neither ns_requested() nor may_list_ns() needs a reference, both

only look at the namespace type and at the caller's own namespaces, so do

the checks first and take the reference last.

Splat:

Voluntary context switch within RCU read-side critical section!

WARNING: kernel/rcu/tree_plugin.h:332 at rcu_note_context_switch+0x238/0x2a0, CPU#5: a/3442

CPU: 5 UID: 1000 PID: 3442 Comm: a Not tainted 7.0.0-30-generic #30-Ubuntu P

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References