Public bug reported:

It is super easy to madvise the VDSO with MADV_HWPOISON and this causes
breakage across all userspace. It can be also run inside a root
container, for example inside lxd and this causes out-side-of-container
userspace breakage too.

Example:

inside a container
# gcc vdso.c -o vdso
# ./vdso

and nothing works outside the container too:

ls
Bus error (core dumped)

mainly because the vdso now generates MCE errors when the page is
accessed.


Recommend not allowing madvise on vdso page

vdso source:

https://github.com/ColinIanKing/vdso/blob/master/vdso.c

** Affects: linux (Ubuntu)
     Importance: Critical
         Status: New

** Changed in: linux (Ubuntu)
   Importance: Undecided => Critical

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https://bugs.launchpad.net/bugs/2121542

Title:
  MADV_HWPOISON on vdso is pretty dire, can be done within a container
  for system denial of service attack

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