On Tue, Mar 16, 2021 at 3:44 AM Walter Wu <walter-zh...@mediatek.com> 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 <walter-zh...@mediatek.com> > Suggested-by: Dmitry Vyukov <dvyu...@google.com> > Cc: Andrey Konovalov <andreyk...@google.com> > Cc: Andrey Ryabinin <ryabinin....@gmail.com> > Cc: Dmitry Vyukov <dvyu...@google.com> > Cc: Alexander Potapenko <gli...@google.com> > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: Matthias Brugger <matthias....@gmail.com> > Cc: Jens Axboe <ax...@kernel.dk> > Cc: Oleg Nesterov <o...@redhat.com> > --- > > 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 <andreyk...@google.com>
