[PATCH 1/2] mm/kasan: dump alloc/free stack for page allocator

[Walter Wu]

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

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

This feature depends on page owner to record the last stack of pages.
It is very helpful for solving the page use-after-free or out-of-bound.

KASAN report will show the last stack of page, it may be:
a) If page is in-use state, then it prints alloc stack.
   It is useful to fix up page out-of-bound issue.

BUG: KASAN: slab-out-of-bounds in kmalloc_pagealloc_oob_right+0x88/0x90
Write of size 1 at addr ffffffc0d64ea00a by task cat/115
...
Allocation stack of page:
 prep_new_page+0x1a0/0x1d8
 get_page_from_freelist+0xd78/0x2748
 __alloc_pages_nodemask+0x1d4/0x1978
 kmalloc_order+0x28/0x58
 kmalloc_order_trace+0x28/0xe0
 kmalloc_pagealloc_oob_right+0x2c/0x90

b) If page is freed state, then it prints free stack.
   It is useful to fix up page use-after-free issue.

BUG: KASAN: use-after-free in kmalloc_pagealloc_uaf+0x70/0x80
Write of size 1 at addr ffffffc0d651c000 by task cat/115
...
Free stack of page:
 kasan_free_pages+0x68/0x70
 __free_pages_ok+0x3c0/0x1328
 __free_pages+0x50/0x78
 kfree+0x1c4/0x250
 kmalloc_pagealloc_uaf+0x38/0x80


This has been discussed, please refer below link.
https://bugzilla.kernel.org/show_bug.cgi?id=203967

Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx>
---
 lib/Kconfig.kasan | 9 +++++++++
 mm/kasan/common.c | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 4fafba1a923b..ba17f706b5f8 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -135,6 +135,15 @@ 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 page last stack information"
+	depends on KASAN && PAGE_OWNER
+	help
+	  By default, KASAN doesn't record alloc/free stack for page allocator.
+	  It is difficult to fix up page use-after-free issue.
+	  This feature depends on page owner to record the last stack of page.
+	  It is very helpful for solving the page use-after-free or out-of-bound.
+
 config TEST_KASAN
 	tristate "Module for testing KASAN for bug detection"
 	depends on m && KASAN
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 2277b82902d8..2a32474efa74 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -35,6 +35,7 @@
 #include <linux/vmalloc.h>
 #include <linux/bug.h>
 #include <linux/uaccess.h>
+#include <linux/page_owner.h>
 
 #include "kasan.h"
 #include "../slab.h"
@@ -227,6 +228,11 @@ void kasan_alloc_pages(struct page *page, unsigned int order)
 
 void kasan_free_pages(struct page *page, unsigned int order)
 {
+#ifdef CONFIG_KASAN_DUMP_PAGE
+	gfp_t gfp_flags = GFP_KERNEL;
+
+	set_page_owner(page, order, gfp_flags);
+#endif
 	if (likely(!PageHighMem(page)))
 		kasan_poison_shadow(page_address(page),
 				PAGE_SIZE << order,
-- 
2.18.0