4.14-stable review patch. If anyone has any objections, please let me know.
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From: Dave Hansen dave.hansen@linux.intel.com
commit 262b6b30087246abf09d6275eb0c0dc421bcbe38 upstream.
This is another case similar to what EFI does: create a new set of page tables, map some code at a low address, and jump to it. PTI mistakes this low address for userspace and mistakenly marks it non-executable in an effort to make it unusable for userspace.
Undo the poison to allow execution.
Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig") Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Signed-off-by: Andrea Arcangeli aarcange@redhat.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: Alan Cox gnomes@lxorguk.ukuu.org.uk Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Jon Masters jcm@redhat.com Cc: Dave Hansen dave.hansen@intel.com Cc: Andi Kleen andi@firstfloor.org Cc: Jeff Law law@redhat.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Greg Kroah-Hartman gregkh@linux-foundation.org Cc: David dwmw@amazon.co.uk Cc: Nick Clifton nickc@redhat.com Link: https://lkml.kernel.org/r/20180108102805.GK25546@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kernel/tboot.c | 1 + 1 file changed, 1 insertion(+)
--- a/arch/x86/kernel/tboot.c +++ b/arch/x86/kernel/tboot.c @@ -127,6 +127,7 @@ static int map_tboot_page(unsigned long p4d = p4d_alloc(&tboot_mm, pgd, vaddr); if (!p4d) return -1; + pgd->pgd &= ~_PAGE_NX; pud = pud_alloc(&tboot_mm, p4d, vaddr); if (!pud) return -1;