lkml.org 
[lkml]   [2018]   [Jul]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3/3] x86/kexec: Allocate 8k PGDs for PTI
Date
From: Joerg Roedel <jroedel@suse.de>

Fuzzing the PTI-x86-32 code with trinity showed unhandled
kernel paging request oops-messages that looked a lot like
silent data corruption.

Lot's of debugging and testing lead to the kexec-32bit code,
which is still allocating 4k PGDs when PTI is enabled. But
since it uses native_set_pud() to build the page-table, it
will unevitably call into __pti_set_user_pgtbl(), which
writes beyond the allocated 4k page.

Use PGD_ALLOCATION_ORDER to allocate PGDs in the kexec code
to fix the issue.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/kernel/machine_kexec_32.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index d1ab07e..5409c28 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -56,7 +56,7 @@ static void load_segments(void)

static void machine_kexec_free_page_tables(struct kimage *image)
{
- free_page((unsigned long)image->arch.pgd);
+ free_pages((unsigned long)image->arch.pgd, PGD_ALLOCATION_ORDER);
image->arch.pgd = NULL;
#ifdef CONFIG_X86_PAE
free_page((unsigned long)image->arch.pmd0);
@@ -72,7 +72,8 @@ static void machine_kexec_free_page_tables(struct kimage *image)

static int machine_kexec_alloc_page_tables(struct kimage *image)
{
- image->arch.pgd = (pgd_t *)get_zeroed_page(GFP_KERNEL);
+ image->arch.pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
+ PGD_ALLOCATION_ORDER);
#ifdef CONFIG_X86_PAE
image->arch.pmd0 = (pmd_t *)get_zeroed_page(GFP_KERNEL);
image->arch.pmd1 = (pmd_t *)get_zeroed_page(GFP_KERNEL);
--
2.7.4
\
 
 \ /
  Last update: 2018-07-25 17:48    [W:0.179 / U:0.420 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site