x86/mm/64: Tighten up vmalloc_fault() sanity checks on 5-level kernels (36b3a772) · Commits · 戴 / test

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: ("x86/mm/vmalloc: Add 5-level paging support") Signed-off-by:

Andy Lutomirski <luto@kernel.org> Signed-off-by:

Thomas 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

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);

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