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 Ryabinin <[email protected]> Cc: Dmitry Vyukov <[email protected]> Cc: Andrey Konovalov <[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]> --- 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..f255294377da 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -55,6 +55,9 @@ int task_work_add(struct task_struct *task, struct callback_head *work, break; } + /* record the work call stack in order to print it in KASAN reports */ + kasan_record_aux_stack(work); + return 0; } diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 3436c6bf7c0c..d300fe9415bd 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. + * 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
