arm64: Make sure permission updates happen for pmd/pud (82034c23) · Commits · 戴 / test

Commit ("arm64: Enforce BBM for huge IO/VMAP mappings") disallowed block mappings for ioremap since that code does not honor break-before-make. The same APIs are also used for permission updating though and the extra checks prevent the permission updates from happening, even though this should be permitted. This results in read-only permissions not being fully applied. Visibly, this can occasionaly be seen as a failure on the built in rodata test when the test data ends up in a section or as an odd RW gap on the page table dump. Fix this by using pgattr_change_is_safe instead of p*d_present for determining if the change is permitted. Reviewed-by:

Kees Cook <keescook@chromium.org> Tested-by:

Peter Robinson <pbrobinson@gmail.com> Reported-by:

Peter Robinson <pbrobinson@gmail.com> Fixes: ("arm64: Enforce BBM for huge IO/VMAP mappings") Signed-off-by:

Laura Abbott <labbott@redhat.com> Signed-off-by:

Will Deacon <will.deacon@arm.com>

arch/arm64/mm/mmu.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -933,13 +933,15 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
		{
		pgprot_t sect_prot = __pgprot(PUD_TYPE_SECT \|
		pgprot_val(mk_sect_prot(prot)));
		pud_t new_pud = pfn_pud(__phys_to_pfn(phys), sect_prot);

		/* ioremap_page_range doesn't honour BBM */
		if (pud_present(READ_ONCE(*pudp)))
		/* Only allow permission changes for now */
		if (!pgattr_change_is_safe(READ_ONCE(pud_val(*pudp)),
		pud_val(new_pud)))
		return 0;

		BUG_ON(phys & ~PUD_MASK);
		set_pud(pudp, pfn_pud(__phys_to_pfn(phys), sect_prot));
		set_pud(pudp, new_pud);
		return 1;
		}

		@@ -947,13 +949,15 @@ int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
		{
		pgprot_t sect_prot = __pgprot(PMD_TYPE_SECT \|
		pgprot_val(mk_sect_prot(prot)));
		pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), sect_prot);

		/* ioremap_page_range doesn't honour BBM */
		if (pmd_present(READ_ONCE(*pmdp)))
		/* Only allow permission changes for now */
		if (!pgattr_change_is_safe(READ_ONCE(pmd_val(*pmdp)),
		pmd_val(new_pmd)))
		return 0;

		BUG_ON(phys & ~PMD_MASK);
		set_pmd(pmdp, pfn_pmd(__phys_to_pfn(phys), sect_prot));
		set_pmd(pmdp, new_pmd);
		return 1;
		}

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