In the Linux kernel, the following vulnerability has been resolved: apparmor: fix: limit the number of levels of policy namespaces Currently the number of policy namespaces is not bounded relying on the user namespace limit. However policy namespaces aren't strictly tied to user namespaces and it is possible to create them and nest them arbitrarily deep which can be used to exhaust system resource. Hard cap policy namespaces to the same depth as user namespaces.
References 8
https://git.kernel.org/stable/c/306039414932c80f8420695a24d4fe10c84ccfb2
416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/3f8699b3ee0c04b4b9bc27b82cd89a40e81e1d2e
416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/6b396cc2f0365e684fc1d3547d18ef79fcee225d
416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/7b6495ead2c611647f6b11441a852324e3eb8616
416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/853ce31ca72097d23991a06876a2ccb5cb64b603
416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/87d0cecc900e55d55fc4dbfb43ac93e269c7a5b3
416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/b1226e37eb3754d389721c135db6107db94c7a72
416baaa9-dc9f-4396-8d5f-8c081fb06d67
https://git.kernel.org/stable/c/d42b2b6bb77ca40ee34ab74ad79305840b5f315d
416baaa9-dc9f-4396-8d5f-8c081fb06d67