Re: [PATCH] ACPICA: Fix use-after-free in acpi_ps_parse_aml()

[Rafael J. Wysocki]

On Fri, Oct 28, 2022 at 5:46 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> On Wed, Oct 19, 2022 at 9:38 AM Chen Zhongjin <chenzhongjin@xxxxxxxxxx> wrote:
> >
> > KASAN reports a use-after-free problem and causes kernel panic
> > triggered by: modprobe acpiphp_ibm
> >
> > BUG: KASAN:
> > use-after-free in acpi_ds_dump_method_stack (drivers/acpi/acpica/dsdebug.c:145)
> > Read of size 8 at addr ffff888002f843f0 by task modprobe/519
> >
> > CPU: 2 PID: 519 Comm: modprobe Not tainted 6.0.0+
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
> >     Call Trace:
> >     <TASK>
> >     acpi_ds_dump_method_stack (drivers/acpi/acpica/dsdebug.c:145)
> >     acpi_ds_method_error (drivers/acpi/acpica/dsmethod.c:232)
> >     acpi_ps_parse_aml (drivers/acpi/acpica/psparse.c:607)
> >     ...
> >     </TASK>
> >
> >     Allocated by task 519:
> >     ...
> >     __kasan_kmalloc (mm/kasan/common.c:526)
> >     acpi_ds_create_walk_state (drivers/acpi/acpica/dswstate.c:519)
> >     acpi_ds_call_control_method (drivers/acpi/acpica/dsmethod.c:498)
> >     acpi_ps_parse_aml (drivers/acpi/acpica/psparse.c:607)
> >     ...
> >
> >     Freed by task 519:
> >     ...
> >     __kmem_cache_free+0xb6/0x3c0
> >     acpi_ds_delete_walk_state (drivers/acpi/acpica/dswstate.c:722)
> >     acpi_ds_call_control_method (drivers/acpi/acpica/dsmethod.c:586)
> >     acpi_ps_parse_aml (drivers/acpi/acpica/psparse.c:607)
> >     ...
> > ---[ end Kernel panic - not syncing: Fatal exception ]---
> >
> > In the error path in acpi_ps_parse_aml():
> >
> >     acpi_ds_call_control_method()
> >         acpi_ds_create_walk_state()
> >             acpi_ds_push_walk_state()
> >             # thread->walk_state_list = walk_state
> >
> >         acpi_ds_init_aml_walk # *fail*
> >         goto cleanup:
> >         acpi_ds_delete_walk_state() # ACPI_FREE(walk_state)
> >
> >     acpi_ds_method_error()
> >         acpi_ds_dump_method_stack()
> >         # using freed thread->walk_state_list
> >
> > Briefly, the walk_state is pushed to thread, and freed without being poped.
> > Then it is used in acpi_ds_dump_method_stack() and causes use-after-free.
> >
> > Add acpi_ds_pop_walk_state(thread) to the error path to fix the problem.
> >
> > Fixes: 0bac4295526c ("ACPICA: Dispatcher: Move stack traversal code to dispatcher")
> >
> > Signed-off-by: Chen Zhongjin <chenzhongjin@xxxxxxxxxx>
>
> This should be submitted to the upstream project on GitHub, but it
> looks bad enough, so I'll take care of this.
>
> Applied as 6.1-rc material, thanks!
>
> > ---
> >  drivers/acpi/acpica/dsmethod.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/acpi/acpica/dsmethod.c b/drivers/acpi/acpica/dsmethod.c
> > index ae2e768830bf..19da7fc73186 100644
> > --- a/drivers/acpi/acpica/dsmethod.c
> > +++ b/drivers/acpi/acpica/dsmethod.c
> > @@ -581,6 +581,7 @@ acpi_ds_call_control_method(struct acpi_thread_state *thread,
> >
> >         acpi_ds_terminate_control_method(obj_desc, next_walk_state);
> >         acpi_ds_delete_walk_state(next_walk_state);
> > +       acpi_ds_pop_walk_state(thread);

On second thought, though, should it be popped before deleting?
Otherwise it looks like there will be still use-after-free, because
acpi_ds_pop_walk_state() accesses the walk_state at the top of the
queue.

Moreover, it is not correct to pop the walk state if next_walk_state
is NULL AFAICS.

I'm dropping this one.


> >
> >         return_ACPI_STATUS(status);
> >  }
> > --
>
> Bob, this looks correct to me, but I may be missing something in which
> case please let me know.