From: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Subject: kasan: record task_work_add() call stack Why record task_work_add() call stack? Syzbot reports many use-after-free issues for task_work, see [1]. After seeing the free stack and the current auxiliary stack, we think they are useless, we don't know where the work was registered. This work may be the free call stack, so we miss the root cause and don't solve the use-after-free. Add the task_work_add() call stack into the KASAN auxiliary stack in order to improve KASAN reports. It helps programmers solve use-after-free issues. [1]: https://groups.google.com/g/syzkaller-bugs/search?q=kasan%20use-after-free%20task_work_run Link: https://lkml.kernel.org/r/20210316024410.19967-1-walter-zh.wu@xxxxxxxxxxxx Signed-off-by: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Suggested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reviewed-by: Jens Axboe <axboe@xxxxxxxxx> Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx> Acked-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/task_work.c | 3 +++ mm/kasan/kasan.h | 2 +- 2 files changed, 4 insertions(+), 1 deletion(-) --- a/kernel/task_work.c~task_work-kasan-record-task_work_add-call-stack +++ a/kernel/task_work.c @@ -34,6 +34,9 @@ int task_work_add(struct task_struct *ta { 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)) --- a/mm/kasan/kasan.h~task_work-kasan-record-task_work_add-call-stack +++ a/mm/kasan/kasan.h @@ -163,7 +163,7 @@ 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]; _
