Re: [PATCH] acpi: Fix use-after-free in acpi_ipmi.c

[Youling Tang]

Hi，
On 11/25/2020 11:53 PM, Rafael J. Wysocki wrote:
> On Tue, Nov 24, 2020 at 1:51 PM Youling Tang <tangyouling@xxxxxxxxxxx> wrote:
> > kfree() has been called inside put_device so anther kfree would cause a
> > use-after-free bug.
> >
> > Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxxx>
> > ---
> >   drivers/acpi/acpi_ipmi.c | 2 --
> >   1 file changed, 2 deletions(-)
> >
> > diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
> > index 9d6c0fc..72902b6 100644
> > --- a/drivers/acpi/acpi_ipmi.c
> > +++ b/drivers/acpi/acpi_ipmi.c
> > @@ -130,7 +130,6 @@ ipmi_dev_alloc(int iface, struct device *dev, acpi_handle handle)
> >                                 ipmi_device, &user);
> >          if (err) {
> >                  put_device(dev);
> > -               kfree(ipmi_device);
> dev doesn't point to the same object in memory as ipmi_device, though,
> if I'm not mistaken.
>
> Please double check that and resend the patch if you are sure that it
> is correct.
You're right, dev really doesn't point to the same memory object
as ipmi_device. I'll send v2 later.

Thanks,
Youling.
> >                  return NULL;
> >          }
> >          ipmi_device->user_interface = user;
> > @@ -142,7 +141,6 @@ static void ipmi_dev_release(struct acpi_ipmi_device *ipmi_device)
> >   {
> >          ipmi_destroy_user(ipmi_device->user_interface);
> >          put_device(ipmi_device->dev);
> > -       kfree(ipmi_device);
> >   }
> >
> >   static void ipmi_dev_release_kref(struct kref *kref)
> > --
> > 2.1.0