queue-4.19/arm64-kaslr-reserve-size-of-arm64_memstart_align-in-.patch

   1 From 47ed7d6da8d07637f01dab77a252bc36fe19dfcb Mon Sep 17 00:00:00 2001
   2 From: Yueyi Li <liyueyi@live.com>
   3 Date: Mon, 24 Dec 2018 07:40:07 +0000
   4 Subject: arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in linear region
   5
   6 [ Upstream commit c8a43c18a97845e7f94ed7d181c11f41964976a2 ]
   7
   8 When KASLR is enabled (CONFIG_RANDOMIZE_BASE=y), the top 4K of kernel
   9 virtual address space may be mapped to physical addresses despite being
  10 reserved for ERR_PTR values.
  11
  12 Fix the randomization of the linear region so that we avoid mapping the
  13 last page of the virtual address space.
  14
  15 Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
  16 Signed-off-by: liyueyi <liyueyi@live.com>
  17 [will: rewrote commit message; merged in suggestion from Ard]
  18 Signed-off-by: Will Deacon <will.deacon@arm.com>
  19 Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
  20 ---
  21  arch/arm64/mm/init.c | 2 +-
  22  1 file changed, 1 insertion(+), 1 deletion(-)
  23
  24 diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
  25 index 787e27964ab9..774c3e17c798 100644
  26 --- a/arch/arm64/mm/init.c
  27 +++ b/arch/arm64/mm/init.c
  28 @@ -450,7 +450,7 @@ void __init arm64_memblock_init(void)
  29                  * memory spans, randomize the linear region as well.
  30                  */
  31                 if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
  32 -                       range = range / ARM64_MEMSTART_ALIGN + 1;
  33 +                       range /= ARM64_MEMSTART_ALIGN;
  34                         memstart_addr -= ARM64_MEMSTART_ALIGN *
  35                                          ((range * memstart_offset_seed) >> 16);
  36                 }
  37 --
  38 2.19.1
  39