Messages in this thread | | | Date | Thu, 1 Oct 2015 11:03:21 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: rwx mapping between ex_table and rodata |
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On Mon, 28 Sep 2015, Kees Cook wrote: > > --- a/arch/x86/mm/init_64.c > > +++ b/arch/x86/mm/init_64.c > > @@ -1132,7 +1132,7 @@ void mark_rodata_ro(void) > > * has been zapped already via cleanup_highmem(). > > */ > > all_end = roundup((unsigned long)_brk_end, PMD_SIZE); > > - set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT); > > + set_memory_nx(text_end, (all_end - text_end) >> PAGE_SHIFT); > > > > rodata_test(); > > > > > > That should work, yeah. I'd still like to find the default permissions > and make them W+nx, though. Regardless, let's get the above added.
The default permissions are set at boot time when setting up the early page tables. When we split them up later on we inherit the PTE bits and then we do that _ro/nx cleanup after the overall layout has been settled.
We can't make them W+nx in the early setup without shooting ourself in the foot, because we only set up at the pud/pmd level.
Thanks,
tglx
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