Re: [PATCH v2 1/1] userfaultfd/sysctl: add vm.unprivileged_userfaultfd

[Peter Xu]

On Wed, May 27, 2020 at 02:54:13PM +0800, Xiaoming Ni wrote:
> 
> On Tue, Mar 19, 2019 at 11:07:22AM +0800, Peter Xu wrote:
> > Add a global sysctl knob "vm.unprivileged_userfaultfd" to control
> > whether userfaultfd is allowed by unprivileged users.  When this is
> > set to zero, only privileged users (root user, or users with the
> > CAP_SYS_PTRACE capability) will be able to use the userfaultfd
> > syscalls.
> 
> Hello

Hi, Xiaoming,

> I am a bit confused about this patch, can you help to answer it.
> 
> Why the sysctl interface of fs/userfaultfd.c belongs to vm_table instead of
> fs_table ?
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cefdca0a86be517bc390fc4541e3674b8e7803b0

Because I think it makes more sense to put the new key into where it suites
better, irrelevant to which directory the variable is declared.  To me,
unprivileged_userfaultfd is definitely more suitable for vm rather than fs,
because userfaultfd is really about memory management rather than file system.

Thanks,

-- 
Peter Xu