[Devel] [PATCH RHEL7 COMMIT] ms/x86/kasan: Fix KASAN shadow region page tables

Konstantin Khorenko khorenko at virtuozzo.com
Thu Sep 3 08:27:50 PDT 2015


The commit is pushed to "branch-rh7-3.10.0-229.7.2-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-229.7.2.vz7.6.6
------>
commit 71bad1e5d1a2aa16ce31dc1413d36d066e73b7e4
Author: Andrey Ryabinin <aryabinin at odin.com>
Date:   Thu Sep 3 19:27:50 2015 +0400

    ms/x86/kasan: Fix KASAN shadow region page tables
    
    https://jira.sw.ru/browse/PSBM-26429
    
    From: Alexander Popov <alpopov at ptsecurity.com>
    
    commit 5d5aa3cfca5cf74cd928daf3674642e6004328d1 upstream.
    
    Currently KASAN shadow region page tables created without
    respect of physical offset (phys_base). This causes kernel halt
    when phys_base is not zero.
    
    So let's initialize KASAN shadow region page tables in
    kasan_early_init() using __pa_nodebug() which considers
    phys_base.
    
    This patch also separates x86_64_start_kernel() from KASAN low
    level details by moving kasan_map_early_shadow(init_level4_pgt)
    into kasan_early_init().
    
    Remove the comment before clear_bss() which stopped bringing
    much profit to the code readability. Otherwise describing all
    the new order dependencies would be too verbose.
    
    Signed-off-by: Alexander Popov <alpopov at ptsecurity.com>
    Signed-off-by: Andrey Ryabinin <a.ryabinin at samsung.com>
    Cc: <stable at vger.kernel.org> # 4.0+
    Cc: Alexander Potapenko <glider at google.com>
    Cc: Andrey Konovalov <adech.fo at gmail.com>
    Cc: Borislav Petkov <bp at alien8.de>
    Cc: Dmitry Vyukov <dvyukov at google.com>
    Cc: Linus Torvalds <torvalds at linux-foundation.org>
    Cc: Peter Zijlstra <peterz at infradead.org>
    Cc: Thomas Gleixner <tglx at linutronix.de>
    Link: http://lkml.kernel.org/r/1435828178-10975-3-git-send-email-a.ryabinin@samsung.com
    Signed-off-by: Ingo Molnar <mingo at kernel.org>
    Signed-off-by: Andrey Ryabinin <aryabinin at odin.com>
    
    Signed-off-by: Andrey Ryabinin <aryabinin at odin.com>
---
 arch/x86/include/asm/kasan.h |  8 ++------
 arch/x86/kernel/head64.c     |  7 ++-----
 arch/x86/kernel/head_64.S    | 28 ----------------------------
 arch/x86/mm/kasan_init_64.c  | 36 ++++++++++++++++++++++++++++++++++--
 4 files changed, 38 insertions(+), 41 deletions(-)

diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h
index 8b22422..74a2a8d 100644
--- a/arch/x86/include/asm/kasan.h
+++ b/arch/x86/include/asm/kasan.h
@@ -14,15 +14,11 @@
 
 #ifndef __ASSEMBLY__
 
-extern pte_t kasan_zero_pte[];
-extern pte_t kasan_zero_pmd[];
-extern pte_t kasan_zero_pud[];
-
 #ifdef CONFIG_KASAN
-void __init kasan_map_early_shadow(pgd_t *pgd);
+void __init kasan_early_init(void);
 void __init kasan_init(void);
 #else
-static inline void kasan_map_early_shadow(pgd_t *pgd) { }
+static inline void kasan_early_init(void) { }
 static inline void kasan_init(void) { }
 #endif
 
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 357ce8a..c2dd757 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -159,13 +159,12 @@ void __init x86_64_start_kernel(char * real_mode_data)
 	/* Kill off the identity-map trampoline */
 	reset_early_page_tables();
 
-	kasan_map_early_shadow(early_level4_pgt);
-
-	/* clear bss before set_intr_gate with early_idt_handler */
 	clear_bss();
 
 	clear_page(init_level4_pgt);
 
+	kasan_early_init();
+
 	for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
 		set_intr_gate(i, early_idt_handlers[i]);
 	load_idt((const struct desc_ptr *)&idt_descr);
@@ -183,8 +182,6 @@ void __init x86_64_start_kernel(char * real_mode_data)
 	/* set init_level4_pgt kernel high mapping*/
 	init_level4_pgt[511] = early_level4_pgt[511];
 
-	kasan_map_early_shadow(init_level4_pgt);
-
 	x86_64_start_reservations(real_mode_data);
 }
 
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 4178929..cb5bf29 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -514,22 +514,6 @@ ENTRY(phys_base)
 	/* This must match the first entry in level2_kernel_pgt */
 	.quad   0x0000000000000000
 
-#ifdef CONFIG_KASAN
-#define FILL(VAL, COUNT)				\
-	.rept (COUNT) ;					\
-	.quad	(VAL) ;					\
-	.endr
-
-NEXT_PAGE(kasan_zero_pte)
-	FILL(kasan_zero_page - __START_KERNEL_map + _KERNPG_TABLE, 512)
-NEXT_PAGE(kasan_zero_pmd)
-	FILL(kasan_zero_pte - __START_KERNEL_map + _KERNPG_TABLE, 512)
-NEXT_PAGE(kasan_zero_pud)
-	FILL(kasan_zero_pmd - __START_KERNEL_map + _KERNPG_TABLE, 512)
-
-#undef FILL
-#endif
-
 #include "../../x86/xen/xen-head.S"
 	
 	.section .bss, "aw", @nobits
@@ -551,15 +535,3 @@ ENTRY(trace_idt_table)
 NEXT_PAGE(empty_zero_page)
 	.skip PAGE_SIZE
 
-#ifdef CONFIG_KASAN
-/*
- * This page used as early shadow. We don't use empty_zero_page
- * at early stages, stack instrumentation could write some garbage
- * to this page.
- * Latter we reuse it as zero shadow for large ranges of memory
- * that allowed to access, but not instrumented by kasan
- * (vmalloc/vmemmap ...).
- */
-NEXT_PAGE(kasan_zero_page)
-	.skip PAGE_SIZE
-#endif
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 7620537..ad0b931 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -11,7 +11,19 @@
 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
 extern struct range pfn_mapped[E820_X_MAX];
 
-extern unsigned char kasan_zero_page[PAGE_SIZE];
+static pud_t kasan_zero_pud[PTRS_PER_PUD] __page_aligned_bss;
+static pmd_t kasan_zero_pmd[PTRS_PER_PMD] __page_aligned_bss;
+static pte_t kasan_zero_pte[PTRS_PER_PTE] __page_aligned_bss;
+
+/*
+ * This page used as early shadow. We don't use empty_zero_page
+ * at early stages, stack instrumentation could write some garbage
+ * to this page.
+ * Latter we reuse it as zero shadow for large ranges of memory
+ * that allowed to access, but not instrumented by kasan
+ * (vmalloc/vmemmap ...).
+ */
+static unsigned char kasan_zero_page[PAGE_SIZE] __page_aligned_bss;
 
 static int __init map_range(struct range *range)
 {
@@ -36,7 +48,7 @@ static void __init clear_pgds(unsigned long start,
 		pgd_clear(pgd_offset_k(start));
 }
 
-void __init kasan_map_early_shadow(pgd_t *pgd)
+static void __init kasan_map_early_shadow(pgd_t *pgd)
 {
 	int i;
 	unsigned long start = KASAN_SHADOW_START;
@@ -166,6 +178,26 @@ static struct notifier_block kasan_die_notifier = {
 };
 #endif
 
+void __init kasan_early_init(void)
+{
+	int i;
+	pteval_t pte_val = __pa_nodebug(kasan_zero_page) | __PAGE_KERNEL;
+	pmdval_t pmd_val = __pa_nodebug(kasan_zero_pte) | _KERNPG_TABLE;
+	pudval_t pud_val = __pa_nodebug(kasan_zero_pmd) | _KERNPG_TABLE;
+
+	for (i = 0; i < PTRS_PER_PTE; i++)
+		kasan_zero_pte[i] = __pte(pte_val);
+
+	for (i = 0; i < PTRS_PER_PMD; i++)
+		kasan_zero_pmd[i] = __pmd(pmd_val);
+
+	for (i = 0; i < PTRS_PER_PUD; i++)
+		kasan_zero_pud[i] = __pud(pud_val);
+
+	kasan_map_early_shadow(early_level4_pgt);
+	kasan_map_early_shadow(init_level4_pgt);
+}
+
 void __init kasan_init(void)
 {
 	int i;



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