[tip:x86/boot] x86/KASLR: Initialize mapping_info every time

[tip-bot for Kees Cook]

Commit-ID:  434a6c9f90f7ab5ade619455df01ef5ebea533ee
Gitweb:     http://git.kernel.org/tip/434a6c9f90f7ab5ade619455df01ef5ebea533ee
Author:     Kees Cook <keescook@xxxxxxxxxxxx>
AuthorDate: Mon, 9 May 2016 13:22:04 -0700
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 10 May 2016 10:12:02 +0200

x86/KASLR: Initialize mapping_info every time

As it turns out, mapping_info DOES need to be initialized every
time, because pgt_data address could be changed during kernel
relocation. So it can not be build time assigned.

Without this, page tables were not being corrected updated, which
could cause reboots when a physical address beyond 2G was chosen.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: kernel-hardening@xxxxxxxxxxxxxxxxxx
Cc: lasse.collin@xxxxxxxxxxx
Link: http://lkml.kernel.org/r/1462825332-10505-2-git-send-email-keescook@xxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/boot/compressed/pagetable.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c
index 3c99051..34b95df 100644
--- a/arch/x86/boot/compressed/pagetable.c
+++ b/arch/x86/boot/compressed/pagetable.c
@@ -90,23 +90,17 @@ static void prepare_level4(void)
 }
 
 /*
- * Mapping information structure passed to kernel_ident_mapping_init().
- * Since this never changes, there's no reason to repeatedly fill it
- * in on the stack when calling add_identity_map().
- */
-static struct x86_mapping_info mapping_info = {
-	.alloc_pgt_page	= alloc_pgt_page,
-	.context	= &pgt_data,
-	.pmd_flag	= __PAGE_KERNEL_LARGE_EXEC,
-};
-
-/*
  * Adds the specified range to what will become the new identity mappings.
  * Once all ranges have been added, the new mapping is activated by calling
  * finalize_identity_maps() below.
  */
 void add_identity_map(unsigned long start, unsigned long size)
 {
+	struct x86_mapping_info mapping_info = {
+		.alloc_pgt_page	= alloc_pgt_page,
+		.context	= &pgt_data,
+		.pmd_flag	= __PAGE_KERNEL_LARGE_EXEC,
+	};
 	unsigned long end = start + size;
 
 	/* Make sure we have a top level page table ready to use. */