Why record task_work_add() call stack?
Syzbot reports many use-after-free issues for task_work, see [1].
After see the free stack and the current auxiliary stack, we think
they are useless, we don't know where register the work, this work
may be the free call stack, so that we miss the root cause and
don't solve the use-after-free.
Add task_work_add() call stack into KASAN auxiliary stack in
order to improve KASAN report. It is useful for programmers
to solve use-after-free issues.
[1]: https://groups.google.com/g/syzkaller-bugs/search?q=kasan%20use-after-free%20task_work_run
Signed-off-by: Walter Wu <[email protected]>
Suggested-by: Dmitry Vyukov <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Matthias Brugger <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Oleg Nesterov <[email protected]>
---
v2: Fix kasan_record_aux_stack() calling sequence issue.
Thanks for Dmitry's suggestion
---
kernel/task_work.c | 3 +++
mm/kasan/kasan.h | 2 +-
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/task_work.c b/kernel/task_work.c
index 9cde961875c0..3d4852891fa8 100644
--- a/kernel/task_work.c
+++ b/kernel/task_work.c
@@ -34,6 +34,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
{
struct callback_head *head;
+ /* record the work call stack in order to print it in KASAN reports */
+ kasan_record_aux_stack(work);
+
do {
head = READ_ONCE(task->task_works);
if (unlikely(head == &work_exited))
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 3436c6bf7c0c..e4629a971a3c 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -146,7 +146,7 @@ struct kasan_alloc_meta {
struct kasan_track alloc_track;
#ifdef CONFIG_KASAN_GENERIC
/*
- * call_rcu() call stack is stored into struct kasan_alloc_meta.
+ * The auxiliary stack is stored into struct kasan_alloc_meta.
* The free stack is stored into struct kasan_free_meta.
*/
depot_stack_handle_t aux_stack[2];
--
2.18.0
On 3/15/21 8:44 PM, Walter Wu wrote:
> Why record task_work_add() call stack?
> Syzbot reports many use-after-free issues for task_work, see [1].
> After see the free stack and the current auxiliary stack, we think
> they are useless, we don't know where register the work, this work
> may be the free call stack, so that we miss the root cause and
> don't solve the use-after-free.
>
> Add task_work_add() call stack into KASAN auxiliary stack in
> order to improve KASAN report. It is useful for programmers
> to solve use-after-free issues.
I think this is a very useful addition, especially as task_work
proliferates.
Reviewed-by: Jens Axboe <[email protected]>
--
Jens Axboe
On 03/16, Walter Wu wrote:
>
> --- a/kernel/task_work.c
> +++ b/kernel/task_work.c
> @@ -34,6 +34,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
> {
> struct callback_head *head;
>
> + /* record the work call stack in order to print it in KASAN reports */
> + kasan_record_aux_stack(work);
> +
> do {
> head = READ_ONCE(task->task_works);
> if (unlikely(head == &work_exited))
Acked-by: Oleg Nesterov <[email protected]>
On Tue, Mar 16, 2021 at 3:44 AM Walter Wu <[email protected]> wrote:
>
> Why record task_work_add() call stack?
> Syzbot reports many use-after-free issues for task_work, see [1].
> After see the free stack and the current auxiliary stack, we think
> they are useless, we don't know where register the work, this work
> may be the free call stack, so that we miss the root cause and
> don't solve the use-after-free.
>
> Add task_work_add() call stack into KASAN auxiliary stack in
> order to improve KASAN report. It is useful for programmers
> to solve use-after-free issues.
>
> [1]: https://groups.google.com/g/syzkaller-bugs/search?q=kasan%20use-after-free%20task_work_run
>
> Signed-off-by: Walter Wu <[email protected]>
> Suggested-by: Dmitry Vyukov <[email protected]>
> Cc: Andrey Konovalov <[email protected]>
> Cc: Andrey Ryabinin <[email protected]>
> Cc: Dmitry Vyukov <[email protected]>
> Cc: Alexander Potapenko <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Matthias Brugger <[email protected]>
> Cc: Jens Axboe <[email protected]>
> Cc: Oleg Nesterov <[email protected]>
> ---
>
> v2: Fix kasan_record_aux_stack() calling sequence issue.
> Thanks for Dmitry's suggestion
>
> ---
> kernel/task_work.c | 3 +++
> mm/kasan/kasan.h | 2 +-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/task_work.c b/kernel/task_work.c
> index 9cde961875c0..3d4852891fa8 100644
> --- a/kernel/task_work.c
> +++ b/kernel/task_work.c
> @@ -34,6 +34,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
> {
> struct callback_head *head;
>
> + /* record the work call stack in order to print it in KASAN reports */
> + kasan_record_aux_stack(work);
> +
> do {
> head = READ_ONCE(task->task_works);
> if (unlikely(head == &work_exited))
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 3436c6bf7c0c..e4629a971a3c 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -146,7 +146,7 @@ struct kasan_alloc_meta {
> struct kasan_track alloc_track;
> #ifdef CONFIG_KASAN_GENERIC
> /*
> - * call_rcu() call stack is stored into struct kasan_alloc_meta.
> + * The auxiliary stack is stored into struct kasan_alloc_meta.
> * The free stack is stored into struct kasan_free_meta.
> */
> depot_stack_handle_t aux_stack[2];
> --
Acked-by: Andrey Konovalov <[email protected]>