Hi
On Mon, Jan 15, 2024 at 10:49 PM Stefan Hajnoczi <stefa...@redhat.com> wrote:
>
> On Fri, Jan 12, 2024 at 07:36:19PM +0900, Akihiko Odaki 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.od...@daynix.com>
Thanks Akihiko, this is solving a crash when enabling ASAN!
> > ---
> > util/coroutine-ucontext.c | 21 +++++++++++++++++++--
> > 1 file changed, 19 insertions(+), 2 deletions(-)
>
> Adding Marc-André Lureau and Lingfeng Yang, who authored the code in
> question.
Side note:
I am surprised that commit 0aebab04b9 "configure: add --enable-tsan
flag + fiber annotations" changed code like this:
{
#ifdef CONFIG_ASAN
- __sanitizer_start_switch_fiber(fake_stack_save, bottom, size);
+ __sanitizer_start_switch_fiber(
+ action == COROUTINE_TERMINATE ? NULL : fake_stack_save,
+ bottom, size);
+#endif
+#ifdef CONFIG_TSAN
+ void *curr_fiber =
+ __tsan_get_current_fiber();
+ __tsan_acquire(curr_fiber);
+
+ *fake_stack_save = curr_fiber;
+ __tsan_switch_to_fiber(new_fiber, 0); /* 0=synchronize */
#endif
*fake_stack_save = curr_fiber:
Is TSAN compatible with ASAN ? I guess not.
It would probably help to have more explicit comments & errors if such
a case happens.
>
> Stefan
>
> >
> > diff --git a/util/coroutine-ucontext.c b/util/coroutine-ucontext.c
> > index 7b304c79d942..e62ced5d6779 100644
> > --- a/util/coroutine-ucontext.c
> > +++ b/util/coroutine-ucontext.c
> > @@ -124,8 +124,9 @@ void start_switch_fiber_asan(CoroutineAction action,
> > void **fake_stack_save,
> > {
> > #ifdef CONFIG_ASAN
> > __sanitizer_start_switch_fiber(
> > - action == COROUTINE_TERMINATE ? NULL : fake_stack_save,
> > - bottom, size);
> > + !IS_ENABLED(CONFIG_COROUTINE_POOL) && action ==
> > COROUTINE_TERMINATE ?
> > + NULL : fake_stack_save,
> > + bottom, size);
Ok, changing back the commit from Lingfeng when coroutine pools are enabled.
> > #endif
> > }
> >
> > @@ -269,10 +270,26 @@ static inline void
> > valgrind_stack_deregister(CoroutineUContext *co)
> > #endif
> > #endif
> >
> > +#if defined(CONFIG_ASAN) && defined(CONFIG_COROUTINE_POOL)
> > +static void coroutine_fn terminate(void *opaque)
> > +{
> > + CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, opaque);
> > +
> > + __sanitizer_start_switch_fiber(NULL, to->stack, to->stack_size);
> > + siglongjmp(to->env, COROUTINE_ENTER);
> > +}
looking at
https://github.com/llvm/llvm-project/blob/main/compiler-rt/test/asan/TestCases/Linux/swapcontext_annotation.cpp,
that seems correct to me to destroy the fake_stack.
However, not switching back with qemu_coroutine_switch() may create
issues: set_current() (and tsan) not being called appropriately.
Should we introduce another action like COROUTINE_DELETE?
> > +#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;
> > + qemu_coroutine_switch(co_->entry_arg, co_, COROUTINE_ENTER);
> > +#endif
> > +
> > #ifdef CONFIG_VALGRIND_H
> > valgrind_stack_deregister(co);
> > #endif
> >
> > ---
> > base-commit: f614acb7450282a119d85d759f27eae190476058
> > change-id: 20240112-asan-eb695c769f40
> >
> > Best regards,
> > --
> > Akihiko Odaki <akihiko.od...@daynix.com>
> >
--
Marc-André Lureau
