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Subject[PATCH v4 4/6] kasan: add tests for timer stack recording
Date
Adds a test to verify timer stack recording and print it
in KASAN report.

The KASAN report was as follows(cleaned up slightly):

BUG: KASAN: use-after-free in kasan_timer_uaf

Freed by task 0:
kasan_save_stack+0x24/0x50
kasan_set_track+0x24/0x38
kasan_set_free_info+0x20/0x40
__kasan_slab_free+0x10c/0x170
kasan_slab_free+0x10/0x18
kfree+0x98/0x270
kasan_timer_function+0x1c/0x28

Last potentially related work creation:
kasan_save_stack+0x24/0x50
kasan_record_tmr_stack+0xa8/0xb8
init_timer_key+0xf0/0x248
kasan_timer_uaf+0x5c/0xd8

Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Acked-by: Marco Elver <elver@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
---

v4:
- testcase has merge conflict, so that rebase onto the KASAN-KUNIT

---
lib/test_kasan_module.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c
index 2d68db6ae67b..d8234a1db8c9 100644
--- a/lib/test_kasan_module.c
+++ b/lib/test_kasan_module.c
@@ -12,6 +12,7 @@
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
+#include <linux/delay.h>

#include "../mm/kasan/kasan.h"

@@ -91,6 +92,29 @@ static noinline void __init kasan_rcu_uaf(void)
call_rcu(&global_rcu_ptr->rcu, kasan_rcu_reclaim);
}

+static noinline void __init kasan_timer_function(struct timer_list *timer)
+{
+ del_timer(timer);
+ kfree(timer);
+}
+
+static noinline void __init kasan_timer_uaf(void)
+{
+ struct timer_list *timer;
+
+ timer = kmalloc(sizeof(struct timer_list), GFP_KERNEL);
+ if (!timer) {
+ pr_err("Allocation failed\n");
+ return;
+ }
+
+ timer_setup(timer, kasan_timer_function, 0);
+ add_timer(timer);
+ msleep(100);
+
+ pr_info("use-after-free on timer\n");
+ ((volatile struct timer_list *)timer)->expires;
+}

static int __init test_kasan_module_init(void)
{
@@ -102,6 +126,7 @@ static int __init test_kasan_module_init(void)

copy_user_test();
kasan_rcu_uaf();
+ kasan_timer_uaf();

kasan_restore_multi_shot(multishot);
return -EAGAIN;
--
2.18.0
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