lkml.org 
[lkml]   [2017]   [Dec]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [patch 05/16] mm: Allow special mappings with user access cleared
On Tue, Dec 12, 2017 at 10:05 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Dec 12, 2017 at 10:00:08AM -0800, Andy Lutomirski wrote:
>> On Tue, Dec 12, 2017 at 9:32 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> > From: Peter Zijstra <peterz@infradead.org>
>> >
>> > In order to create VMAs that are not accessible to userspace create a new
>> > VM_NOUSER flag. This can be used in conjunction with
>> > install_special_mapping() to inject 'kernel' data into the userspace map.
>> >
>> > Similar to how arch_vm_get_page_prot() allows adding _PAGE_flags to
>> > pgprot_t, introduce arch_vm_get_page_prot_excl() which masks
>> > _PAGE_flags from pgprot_t and use this to implement VM_NOUSER for x86.
>>
>> How does this interact with get_user_pages(), etc?
>
> gup would find the page. These patches do in fact rely on that through
> the populate things.
>

Blech. So you can write(2) from the LDT to a file and you can even
sendfile it, perhaps. What happens if it's get_user_page()'d when
modify_ldt() wants to free it?

This patch series scares the crap out of me.

\
 
 \ /
  Last update: 2017-12-12 19:07    [W:0.080 / U:6.848 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site