From: Yueyi Li <liyueyi@live.com>
Date: Mon, 24 Dec 2018 07:40:07 +0000 (+0000)
Subject: arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in linear region
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=8add7054070ab79cb271b336d9660bca0ffcaf85;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in linear region

[ Upstream commit c8a43c18a97845e7f94ed7d181c11f41964976a2 ]

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>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
---

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index caa295cd5d09..9e6c822d458d 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -447,7 +447,7 @@ void __init arm64_memblock_init(void)
 		 * memory spans, randomize the linear region as well.
 		 */
 		if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
-			range = range / ARM64_MEMSTART_ALIGN + 1;
+			range /= ARM64_MEMSTART_ALIGN;
 			memstart_addr -= ARM64_MEMSTART_ALIGN *
 					 ((range * memstart_offset_seed) >> 16);
 		}