Re: [PATCH v2] coroutine-ucontext: Save fake stack for pooled coroutine

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

Hi

On Wed, Jan 17, 2024 at 11:26 AM Marc-André Lureau
<marcandre.lureau@gmail.com> wrote:
>
> Hi
>
> On Wed, Jan 17, 2024 at 11:06 AM Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
> >
> > Coroutine may be pooled even after COROUTINE_TERMINATE if
> > CONFIG_COROUTINE_POOL is enabled and fake stack should be saved in
> > such a case to keep AddressSanitizerUseAfterReturn working. Even worse,
> > I'm seeing stack corruption without fake stack being saved.
> >
> > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> > ---
> > Changes in v2:
> > - Added missing set_current() (Marc-André Lureau)
> > - Added G_STATIC_ASSERT(!IS_ENABLED(CONFIG_TSAN)) (Marc-André Lureau)
> > - Renamed terminate() to terminate_asan() for clarity and consistency.
> > - Changed terminate_asan() to call start_switch_fiber_asan() for
> >   consistency.
> > - Link to v1: https://lore.kernel.org/r/20240112-asan-v1-1-e330f0d0032c@daynix.com
> > ---
> >  util/coroutine-ucontext.c | 35 ++++++++++++++++++++++++++---------
> >  1 file changed, 26 insertions(+), 9 deletions(-)
> >
> > diff --git a/util/coroutine-ucontext.c b/util/coroutine-ucontext.c
> > index 7b304c79d942..8ef603d081ea 100644
> > --- a/util/coroutine-ucontext.c
> > +++ b/util/coroutine-ucontext.c
> > @@ -119,13 +119,11 @@ void finish_switch_fiber(void *fake_stack_save)
> >
> >  /* always_inline is required to avoid TSan runtime fatal errors. */
> >  static inline __attribute__((always_inline))
> > -void start_switch_fiber_asan(CoroutineAction action, void **fake_stack_save,
> > +void start_switch_fiber_asan(void **fake_stack_save,
> >                               const void *bottom, size_t size)
> >  {
> >  #ifdef CONFIG_ASAN
> > -    __sanitizer_start_switch_fiber(
> > -            action == COROUTINE_TERMINATE ? NULL : fake_stack_save,
> > -            bottom, size);
> > +    __sanitizer_start_switch_fiber(fake_stack_save, bottom, size);
> >  #endif
> >  }
> >
> > @@ -165,7 +163,7 @@ static void coroutine_trampoline(int i0, int i1)
> >      if (!sigsetjmp(self->env, 0)) {
> >          CoroutineUContext *leaderp = get_ptr_leader();
> >
> > -        start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save,
> > +        start_switch_fiber_asan(&fake_stack_save,
> >                                  leaderp->stack, leaderp->stack_size);
> >          start_switch_fiber_tsan(&fake_stack_save, self, true); /* true=caller */
> >          siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
> > @@ -226,8 +224,7 @@ Coroutine *qemu_coroutine_new(void)
> >
> >      /* swapcontext() in, siglongjmp() back out */
> >      if (!sigsetjmp(old_env, 0)) {
> > -        start_switch_fiber_asan(COROUTINE_YIELD, &fake_stack_save, co->stack,
> > -                                co->stack_size);
> > +        start_switch_fiber_asan(&fake_stack_save, co->stack, co->stack_size);
> >          start_switch_fiber_tsan(&fake_stack_save,
> >                                  co, false); /* false=not caller */
> >
> > @@ -269,10 +266,28 @@ static inline void valgrind_stack_deregister(CoroutineUContext *co)
> >  #endif
> >  #endif
> >
> > +#if defined(CONFIG_ASAN) && defined(CONFIG_COROUTINE_POOL)
> > +static void coroutine_fn terminate_asan(void *opaque)
> > +{
> > +    CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, opaque);
> > +
> > +    set_current(opaque);
> > +    start_switch_fiber_asan(NULL, to->stack, to->stack_size);
> > +    G_STATIC_ASSERT(!IS_ENABLED(CONFIG_TSAN));
> > +    siglongjmp(to->env, COROUTINE_ENTER);
> > +}
> > +#endif
> > +
> >  void qemu_coroutine_delete(Coroutine *co_)
> >  {
> >      CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
> >
> > +#if defined(CONFIG_ASAN) && defined(CONFIG_COROUTINE_POOL)
> > +    co_->entry_arg = qemu_coroutine_self();
> > +    co_->entry = terminate_asan;
> > +    qemu_coroutine_switch(co_->entry_arg, co_, COROUTINE_ENTER);
> > +#endif
> > +
> >  #ifdef CONFIG_VALGRIND_H
> >      valgrind_stack_deregister(co);
> >  #endif
> > @@ -305,8 +320,10 @@ qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
> >
> >      ret = sigsetjmp(from->env, 0);
> >      if (ret == 0) {
> > -        start_switch_fiber_asan(action, &fake_stack_save, to->stack,
> > -                                to->stack_size);
> > +        start_switch_fiber_asan(IS_ENABLED(CONFIG_COROUTINE_POOL) ||
> > +                                action != COROUTINE_TERMINATE ?
> > +                                    &fake_stack_save : NULL,
> > +                                to->stack, to->stack_size);
>
> given that the coroutine is reentered on delete to clear the fake
> stack, can we just pass &fake_stack_save here?
>

Ah, terminate_asan() is only called when the pool is enabled.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>




-- 
Marc-André Lureau