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SubjectRe: [PATCH v7 04/12] mm: page_alloc: add kasan hooks on alloc and free paths
LGTM

On Mon, Nov 24, 2014 at 9:02 PM, Andrey Ryabinin <a.ryabinin@samsung.com> wrote:
> 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 | 1 +
> mm/kasan/report.c | 7 +++++++
> mm/page_alloc.c | 3 +++
> 6 files changed, 33 insertions(+)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 01c99fe..9714fba 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -30,6 +30,9 @@ 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) {}
> @@ -37,6 +40,9 @@ 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 a857225..a5c8e84 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
> @@ -61,6 +62,7 @@ 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 f77be01..b336073 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);
> +}
> +
> void __asan_load1(unsigned long addr)
> {
> check_memory_region(addr, 1, false);
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 6da1d78..2a6a961 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -6,6 +6,7 @@
> #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 */
> #define KASAN_SHADOW_GAP 0xF9 /* address belongs to shadow memory */
>
> struct access_info {
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 56a2089..8ac3b6b 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -57,6 +57,9 @@ static void print_error_description(struct access_info *info)
> case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
> bug_type = "out of bounds access";
> break;
> + case KASAN_FREE_PAGE:
> + bug_type = "use after free";
> + break;
> case KASAN_SHADOW_GAP:
> bug_type = "wild memory access";
> break;
> @@ -78,6 +81,10 @@ static void print_address_description(struct access_info *info)
> page = virt_to_head_page((void *)info->access_addr);
>
> switch (shadow_val) {
> + case KASAN_FREE_PAGE:
> + dump_page(page, "kasan error");
> + dump_stack();
> + break;
> case KASAN_SHADOW_GAP:
> pr_err("No metainfo is available for this access.\n");
> dump_stack();
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index b0e6eab..3829589 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -58,6 +58,7 @@
> #include <linux/page-debug-flags.h>
> #include <linux/hugetlb.h>
> #include <linux/sched/rt.h>
> +#include <linux/kasan.h>
>
> #include <asm/sections.h>
> #include <asm/tlbflush.h>
> @@ -758,6 +759,7 @@ 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;
> @@ -940,6 +942,7 @@ 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);
> --
> 2.1.3
>


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