On Fri, Jun 17, 2016 at 1:30 PM, Borislav Petkov <[email protected]> wrote: > On Fri, Jun 17, 2016 at 01:00:39PM -0700, Andy Lutomirski wrote: >> It's currently only used in the EFI code, which is safe AFAICT. > > "It is basically useful for a pagetable hierarchy which is not init_mm." > >> Warn if anyone tries to use it on the normal kernel pgd. >> >> Signed-off-by: Andy Lutomirski <[email protected]> >> --- >> arch/x86/mm/pageattr.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c >> index 6a8026918bf6..e9b9c5cedbb8 100644 >> --- a/arch/x86/mm/pageattr.c >> +++ b/arch/x86/mm/pageattr.c >> @@ -1996,6 +1996,9 @@ out: >> void kernel_unmap_pages_in_pgd(pgd_t *root, unsigned long address, >> unsigned numpages) >> { >> + /* Unmapping kernel entries from init_mm's pgd is not allowed. */ >> + WARN_ON(root == init_mm.pgd); > > We can also return and not do the unmapping: > > if (WARN_ON(root == init_mm.pgd)) > return;
I'll do one better: the only function that calls this function is unused. I'll just delete it. --Andy
