diff mbox series

[3/3] x86/kexec: Allocate 8k PGDs for PTI

Message ID 1532533683-5988-4-git-send-email-joro@8bytes.org (mailing list archive)
State New, archived
Headers show
Series PTI x86-32 Updates and Fixes | expand

Commit Message

Joerg Roedel July 25, 2018, 3:48 p.m. UTC
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 mbox series


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,
 #ifdef CONFIG_X86_PAE
 	image->arch.pmd0 = (pmd_t *)get_zeroed_page(GFP_KERNEL);
 	image->arch.pmd1 = (pmd_t *)get_zeroed_page(GFP_KERNEL);