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Commit 36b3a772 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Thomas Gleixner
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x86/mm/64: Tighten up vmalloc_fault() sanity checks on 5-level kernels 



On a 5-level kernel, if a non-init mm has a top-level entry, it needs to
match init_mm's, but the vmalloc_fault() code skipped over the BUG_ON()
that would have checked it.

While we're at it, get rid of the rather confusing 4-level folded "pgd"
logic.

Cleans-up: b50858ce ("x86/mm/vmalloc: Add 5-level paging support")
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Neil Berrington <neil.berrington@datacore.com>
Link: https://lkml.kernel.org/r/2ae598f8c279b0a29baf75df207e6f2fdddc0a1b.1516914529.git.luto@kernel.org
parent 5beda7d5

arch/x86/mm/fault.c

+9 −13
Original line number Diff line number Diff line
@@ -439,19 +439,14 @@ static noinline int vmalloc_fault(unsigned long address) 
	if (pgd_none(*pgd_ref))

		return -1;



	if (CONFIG_PGTABLE_LEVELS > 4) {

		if (pgd_none(*pgd)) {

			set_pgd(pgd, *pgd_ref);

			arch_flush_lazy_mmu_mode();

	} else if (CONFIG_PGTABLE_LEVELS > 4) {

		/*

		 * With folded p4d, pgd_none() is always false, so the pgd may

		 * point to an empty page table entry and pgd_page_vaddr()

		 * will return garbage.

		 *

		 * We will do the correct sanity check on the p4d level.

		 */

		} else {

			BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));

		}

	}



	/* With 4-level paging, copying happens on the p4d level. */

	p4d = p4d_offset(pgd, address);
@@ -459,7 +454,7 @@ static noinline int vmalloc_fault(unsigned long address) 
	if (p4d_none(*p4d_ref))

		return -1;



	if (p4d_none(*p4d)) {

	if (p4d_none(*p4d) && CONFIG_PGTABLE_LEVELS == 4) {

		set_p4d(p4d, *p4d_ref);

		arch_flush_lazy_mmu_mode();

	} else {
@@ -470,6 +465,7 @@ static noinline int vmalloc_fault(unsigned long address) 
	 * Below here mismatches are bugs because these lower tables

	 * are shared:

	 */

	BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4);



	pud = pud_offset(p4d, address);

	pud_ref = pud_offset(p4d_ref, address);