Messages in this thread | | | Date | Tue, 15 Dec 2015 10:40:15 +0100 | From | Pavel Machek <> | Subject | Re: 4.4-rc5: ugly warn on: 5 W+X pages found |
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On Mon 2015-12-14 14:25:10, Andy Lutomirski wrote: > On Mon, Dec 14, 2015 at 1:24 PM, Arjan van de Ven <arjan@linux.intel.com> wrote: > > > >> That's weird. The only API to do that seems to be manually setting > >> kmap_prot to _PAGE_KERNEL_EXEC, and nothing does that. (Why is > >> kmap_prot a variable on x86 at all? It has exactly one writer, and > >> that's the code that initializes it in the first place. Shouldn't we > >> #define kmap_prot _PAGE_KERNEL? > > > > > > iirc it changes based on runtime detection of NX capability > > > > Maybe it did, but if it still does, I can't find the code. > > What *does* change is __supported_pte_mask. If we're willing to make > disable_nx work a little less well, we could try to initialize > __supported_pte_mask from the very beginning. (We currently seem to > detect and enable NX even before we enable paging.) I suspect that > Pavel is seeing a kmap mapping left over from so early that it didn't > have NX set (killed by massage_pgprot).
I tried applying:
[PATCH 1/2] x86_32/mm: Set NX in __supported_pte_mask before enabling paging
but I still get
[ 2.685402] ------------[ cut here ]------------ [ 2.688649] WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:225 note_ page+0x5ec/0x790() [ 2.691897] x86/mm: Found insecure W+X mapping at address ffe69000/0xffe69000 [ 2.695090] Modules linked in:
Best regards, Pavel
-- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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