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powerpc/32s: map kasan zero shadow with PAGE_READONLY instead of PAGE_KERNEL_RO

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For hash32, the zero shadow page gets mapped with PAGE_READONLY instead
of PAGE_KERNEL_RO, because the PP bits don't provide a RO kernel, so
PAGE_KERNEL_RO is equivalent to PAGE_KERNEL. By using PAGE_READONLY,
the page is RO for both kernel and user, but this is not a security issue
as it contains only zeroes.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2019-04-26 16:23:37 +00:00 committed by Michael Ellerman
parent 215b823707
commit da3a3b0a0e
1 changed files with 8 additions and 2 deletions
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10
arch/powerpc/mm/kasan/kasan_init_32.c
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@ -39,7 +39,10 @@ static int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_
if (!new) if (!new)
return -ENOMEM; return -ENOMEM;
kasan_populate_pte(new, PAGE_KERNEL_RO); if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE))
kasan_populate_pte(new, PAGE_READONLY);
else
kasan_populate_pte(new, PAGE_KERNEL_RO);
pmd_populate_kernel(&init_mm, pmd, new); pmd_populate_kernel(&init_mm, pmd, new);
} }
return 0; return 0;
@ -84,7 +87,10 @@ static int __ref kasan_init_region(void *start, size_t size)
static void __init kasan_remap_early_shadow_ro(void) static void __init kasan_remap_early_shadow_ro(void)
{ {
kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL_RO); if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE))
kasan_populate_pte(kasan_early_shadow_pte, PAGE_READONLY);
else
kasan_populate_pte(kasan_early_shadow_pte, PAGE_KERNEL_RO);
flush_tlb_kernel_range(KASAN_SHADOW_START, KASAN_SHADOW_END); flush_tlb_kernel_range(KASAN_SHADOW_START, KASAN_SHADOW_END);
} }