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Date: Thu, 9 Mar 2017 09:25:09 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: linux-arm-kernel@...ts.infradead.org,
mark.rutland@....com,
keescook@...omium.org,
labbott@...oraproject.org
Cc: kernel-hardening@...ts.openwall.com,
will.deacon@....com,
catalin.marinas@....com,
kvmarm@...ts.cs.columbia.edu,
marc.zyngier@....com,
Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH v5 07/10] arm64/mmu: ignore debug_pagealloc for kernel segments
The debug_pagealloc facility manipulates kernel mappings in the linear
region at page granularity to detect out of bounds or use-after-free
accesses. Since the kernel segments are not allocated dynamically,
there is no point in taking the debug_pagealloc_enabled flag into
account for them, and we can use block mappings unconditionally.
Note that this applies equally to the linear alias of text/rodata:
we will never have dynamic allocations there given that the same
memory is statically in use by the kernel image.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
arch/arm64/mm/mmu.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index c3963c592ec3..d3fecd20a136 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -328,8 +328,7 @@ static void update_mapping_prot(phys_addr_t phys, unsigned long virt,
return;
}
- __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
- NULL, debug_pagealloc_enabled());
+ __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL, false);
/* flush the TLBs after updating live kernel mappings */
flush_tlb_kernel_range(virt, virt + size);
@@ -381,7 +380,7 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end
*/
__create_pgd_mapping(pgd, kernel_start, __phys_to_virt(kernel_start),
kernel_end - kernel_start, PAGE_KERNEL,
- early_pgtable_alloc, debug_pagealloc_enabled());
+ early_pgtable_alloc, false);
}
void __init mark_linear_text_alias_ro(void)
@@ -437,7 +436,7 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end,
BUG_ON(!PAGE_ALIGNED(size));
__create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot,
- early_pgtable_alloc, debug_pagealloc_enabled());
+ early_pgtable_alloc, false);
vma->addr = va_start;
vma->phys_addr = pa_start;
--
2.7.4
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