CVE-2026-53341 fhandle: fix UAF due to unlocked ->mnt_ns read in may_decode_fh()

In the Linux kernel, the following vulnerability has been resolved: fhandle: fix UAF due to unlocked -mntns read in maydecodefh maydecodefh accesses mount::mntns without holding any locks; that means the mount can concurrently be unmounted, and the mntnamespace can concurrently be freed after an...