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arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in linear region

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When KASLR is enabled (CONFIG_RANDOMIZE_BASE=y), the top 4K of kernel
virtual address space may be mapped to physical addresses despite being
reserved for ERR_PTR values.

Fix the randomization of the linear region so that we avoid mapping the
last page of the virtual address space.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: liyueyi <liyueyi@live.com>
[will: rewrote commit message; merged in suggestion from Ard]
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Yueyi Li 2018-12-24 07:40:07 +00:00 committed by Will Deacon
parent acafce48b0
commit c8a43c18a9
1 changed files with 1 additions and 1 deletions
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2
arch/arm64/mm/init.c
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@ -457,7 +457,7 @@ void __init arm64_memblock_init(void)
* memory spans, randomize the linear region as well. * memory spans, randomize the linear region as well.
*/ */
if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) { if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
range = range / ARM64_MEMSTART_ALIGN + 1; range /= ARM64_MEMSTART_ALIGN;
memstart_addr -= ARM64_MEMSTART_ALIGN * memstart_addr -= ARM64_MEMSTART_ALIGN *
((range * memstart_offset_seed) >> 16); ((range * memstart_offset_seed) >> 16);
} }