How to change page permission from inside the kernel?

[valdis.kletnieks at vt.edu]

On Fri, 06 Jul 2018 20:06:29 +0200, Ahmed Soliman said:
> I have a memory page allocated with mmap() from user space, This
> address is passed to some kernel module (kvm_intel to be specific) and
> i want to know how can I change the page permission from inside there
> My goal is to achieve something like this
>               mprotect(mem, PAGE_SIZE, PROT_READ)
> except for mprotect can't be called from the kernel, and I couldn't
> find the right way to do it.

You better have a *really* good reason for wanting to do that from inside
the kernel, when userspace is perfectly able to do it for itself.

So there's two questions here:

1) Why does the page's protection need to be changed?
2) And why from inside the kernel?
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 486 bytes
Desc: not available
URL: <http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20180706/190ef547/attachment.sig>