[PATCH v3] mm/kasan: dump alloc and free stack for page allocator

Walter Wu
2019-09-11T08:39:35Z

This patch is KASAN's report adds the alloc/free stack for page allocator
in order to help programmer to see memory corruption caused by the page.

By default, KASAN doesn't record alloc or free stack for page allocator.
It is difficult to fix up the page use-after-free or double-free issue.

We add the following changing:
1) KASAN enable PAGE_OWNER by default to get the alloc stack of the page.
2) Add new feature option to get the free stack of the page.

The new feature KASAN_DUMP_PAGE depends on DEBUG_PAGEALLOC, it will help
to record free stack of the page, it is very helpful for solving the page
use-after-free or double-free issue.

When KASAN_DUMP_PAGE is enabled then KASAN's report will show the last
alloc and free stack of the page, it should be:

BUG: KASAN: use-after-free in kmalloc_pagealloc_uaf+0x70/0x80
Write of size 1 at addr ffffffc0d60e4000 by task cat/115
...
prep_new_page+0x1c8/0x218
get_page_from_freelist+0x1ba0/0x28d0
__alloc_pages_nodemask+0x1d4/0x1978
kmalloc_order+0x28/0x58
kmalloc_order_trace+0x28/0xe0
kmalloc_pagealloc_uaf+0x2c/0x80
page last free stack trace:
__free_pages_ok+0x116c/0x1630
__free_pages+0x50/0x78
kfree+0x1c4/0x250
kmalloc_pagealloc_uaf+0x38/0x80

Changes since v1:
- slim page_owner and move it into kasan
- enable the feature by default

Changes since v2:
- enable PAGE_OWNER by default
- use DEBUG_PAGEALLOC to get page information

cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
cc: Vlastimil Babka <vbabka@suse.cz>
cc: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
---
lib/Kconfig.kasan | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 4fafba1a923b..4d59458c0c5a 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -41,6 +41,7 @@ config KASAN_GENERIC
select SLUB_DEBUG if SLUB
select CONSTRUCTORS
select STACKDEPOT
+ select PAGER_OWNER
help
Enables generic KASAN mode.
Supported in both GCC and Clang. With GCC it requires version 4.9.2
@@ -63,6 +64,7 @@ config KASAN_SW_TAGS
select SLUB_DEBUG if SLUB
select CONSTRUCTORS
select STACKDEPOT
+ select PAGER_OWNER
help
Enables software tag-based KASAN mode.
This mode requires Top Byte Ignore support by the CPU and therefore
@@ -135,6 +137,19 @@ config KASAN_S390_4_LEVEL_PAGING
to 3TB of RAM with KASan enabled). This options allows to force
4-level paging instead.

+config KASAN_DUMP_PAGE
+ bool "Dump the last allocation and freeing stack of the page"
+ depends on KASAN
+ select DEBUG_PAGEALLOC
+ help
+ By default, KASAN enable PAGE_OWNER only to record alloc stack
+ for page allocator. It is difficult to fix up page use-after-free
+ or double-free issue.
+ This feature depends on DEBUG_PAGEALLOC, it will extra record
+ free stack of page. It is very helpful for solving the page
+ use-after-free or double-free issue.
+ This option will have a small memory overhead.
+
config TEST_KASAN
tristate "Module for testing KASAN for bug detection"
depends on m && KASAN
--
2.18.0