CVE-2024-50199

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

mm/swapfile: skip HugeTLB pages for unuse_vma

I got a bad pud error and lost a 1GB HugeTLB when calling swapoff. The problem can be reproduced by the following steps:

1. Allocate an anonymous 1GB HugeTLB and some other anonymous memory.
2. Swapout the above anonymous memory.

3. run swapoff and we will get a bad pud error in kernel message:

   mm/pgtable-generic.c:42: bad pud 00000000743d215d(84000001400000e7)

We can tell that pudclearbad is called by pudnoneorclearbad in unusepudrange() by ftrace. And therefore the HugeTLB pages will never be freed because we lost it from page table. We can skip HugeTLB pages for unuse_vma to fix it.