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Subject[PATCH v10 03/17] mm: page_alloc: add kasan hooks on alloc and free paths
Date
Add kernel address sanitizer hooks to mark allocated page's addresses
as accessible in corresponding shadow region.
Mark freed pages as inaccessible.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
---
include/linux/kasan.h | 6 ++++++
mm/compaction.c | 2 ++
mm/kasan/kasan.c | 14 ++++++++++++++
mm/kasan/kasan.h | 2 ++
mm/kasan/report.c | 11 +++++++++++
mm/page_alloc.c | 3 +++
6 files changed, 38 insertions(+)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index bb72642..ab5131e 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -31,6 +31,9 @@ static inline void kasan_disable_local(void)

void kasan_unpoison_shadow(const void *address, size_t size);

+void kasan_alloc_pages(struct page *page, unsigned int order);
+void kasan_free_pages(struct page *page, unsigned int order);
+
#else /* CONFIG_KASAN */

static inline void kasan_unpoison_shadow(const void *address, size_t size) {}
@@ -38,6 +41,9 @@ static inline void kasan_unpoison_shadow(const void *address, size_t size) {}
static inline void kasan_enable_local(void) {}
static inline void kasan_disable_local(void) {}

+static inline void kasan_alloc_pages(struct page *page, unsigned int order) {}
+static inline void kasan_free_pages(struct page *page, unsigned int order) {}
+
#endif /* CONFIG_KASAN */

#endif /* LINUX_KASAN_H */
diff --git a/mm/compaction.c b/mm/compaction.c
index b68736c..b2d3ef9 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -16,6 +16,7 @@
#include <linux/sysfs.h>
#include <linux/balloon_compaction.h>
#include <linux/page-isolation.h>
+#include <linux/kasan.h>
#include "internal.h"

#ifdef CONFIG_COMPACTION
@@ -72,6 +73,7 @@ static void map_pages(struct list_head *list)
list_for_each_entry(page, list, lru) {
arch_alloc_page(page, 0);
kernel_map_pages(page, 1, 1);
+ kasan_alloc_pages(page, 0);
}
}

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 895fa5f..ea86458 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -247,6 +247,20 @@ static __always_inline void check_memory_region(unsigned long addr,
kasan_report(addr, size, write);
}

+void kasan_alloc_pages(struct page *page, unsigned int order)
+{
+ if (likely(!PageHighMem(page)))
+ kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
+}
+
+void kasan_free_pages(struct page *page, unsigned int order)
+{
+ if (likely(!PageHighMem(page)))
+ kasan_poison_shadow(page_address(page),
+ PAGE_SIZE << order,
+ KASAN_FREE_PAGE);
+}
+
#define DECLARE_ASAN_CHECK(size) \
void __asan_load##size(unsigned long addr) \
{ \
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index da0e53c..0f09fb2 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -6,6 +6,8 @@
#define KASAN_SHADOW_SCALE_SIZE (1UL << KASAN_SHADOW_SCALE_SHIFT)
#define KASAN_SHADOW_MASK (KASAN_SHADOW_SCALE_SIZE - 1)

+#define KASAN_FREE_PAGE 0xFF /* page was freed */
+
struct access_info {
unsigned long access_addr;
unsigned long first_bad_addr;
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 21a9eeb..4e26c68 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -54,6 +54,9 @@ static void print_error_description(struct access_info *info)
shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);

switch (shadow_val) {
+ case KASAN_FREE_PAGE:
+ bug_type = "use after free";
+ break;
case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
bug_type = "out of bounds access";
break;
@@ -69,6 +72,14 @@ static void print_error_description(struct access_info *info)

static void print_address_description(struct access_info *info)
{
+ unsigned long addr = info->access_addr;
+
+ if ((addr >= PAGE_OFFSET) &&
+ (addr < (unsigned long)high_memory)) {
+ struct page *page = virt_to_head_page((void *)addr);
+ dump_page(page, "kasan: bad access detected");
+ }
+
dump_stack();
}

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8d52ab1..31bc2e8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -25,6 +25,7 @@
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/kmemcheck.h>
+#include <linux/kasan.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/pagevec.h>
@@ -787,6 +788,7 @@ static bool free_pages_prepare(struct page *page, unsigned int order)

trace_mm_page_free(page, order);
kmemcheck_free_shadow(page, order);
+ kasan_free_pages(page, order);

if (PageAnon(page))
page->mapping = NULL;
@@ -970,6 +972,7 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,

arch_alloc_page(page, order);
kernel_map_pages(page, 1 << order, 1);
+ kasan_alloc_pages(page, order);

if (gfp_flags & __GFP_ZERO)
prep_zero_page(page, order, gfp_flags);
--
2.2.2


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