CVE-2025-38499clone_private_mnt(): make sure that caller has CAP_SYS_ADMIN in the right userns

Official description

In the Linux kernel, the following vulnerability has been resolved: clone_private_mnt(): make sure that caller has CAP_SYS_ADMIN in the right userns What we want is to verify there is that clone won't expose something hidden by a mount we wouldn't be able to undo. "Wouldn't be able to undo" may be a result of MNT_LOCKED on a child, but it may also come from lacking admin rights in the userns of the namespace mount belongs to. clone_private_mnt() checks the former, but not the latter. There's a number of rather confusing CAP_SYS_ADMIN checks in various userns during the mount, especially with the new mount API; they serve different purposes and in case of clone_private_mnt() they usually, but not always end up covering the missing check mentioned above.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/36fecd740de2d542d2091d65d36554ee2bcf9c65
• https://git.kernel.org/stable/c/d717325b5ecf2a40daca85c61923e17f32306179
• https://git.kernel.org/stable/c/dc6a664089f10eab0fb36b6e4f705022210191d2
• https://git.kernel.org/stable/c/e77078e52fbf018ab986efb3c79065ab35025607
• https://git.kernel.org/stable/c/38628ae06e2a37770cd794802a3f1310cf9846e3
• https://git.kernel.org/stable/c/c28f922c9dcee0e4876a2c095939d77fe7e15116
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
• https://cert-portal.siemens.com/productcert/html/ssa-082556.html