Messages in this thread | | | Date | Thu, 25 Oct 2018 10:26:03 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 2/2] x86/ldt: Unmap PTEs for the slow before freeing LDT |
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On Wed, Oct 24, 2018 at 11:49:17AM -0700, Andy Lutomirski wrote: > On Tue, Oct 23, 2018 at 9:32 AM Kirill A. Shutemov > <kirill.shutemov@linux.intel.com> wrote: > > > > modify_ldt(2) leaves old LDT mapped after we switch over to the new one. > > Memory for the old LDT gets freed and the pages can be re-used. > > > > Leaving the mapping in place can have security implications. The mapping > > is present in userspace copy of page tables and Meltdown-like attack can > > read these freed and possibly reused pages. > > Code looks okay. But: > > > - /* > > - * Did we already have the top level entry allocated? We can't > > - * use pgd_none() for this because it doens't do anything on > > - * 4-level page table kernels. > > - */ > > - pgd = pgd_offset(mm, LDT_BASE_ADDR); > > This looks like an unrelated cleanup. Can it be its own patch?
Okay, I'll move it into a separate patch in v3.
I'll some more time for comments on v2 before respin.
-- Kirill A. Shutemov
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