Re: [PATCH v26 24/30] x86/cet/shstk: Introduce shadow stack token setup/verify routines

Eugene Syromiatnikov
2021-05-18T00:15:06Z

On Mon, May 17, 2021 at 01:55:01PM -0700, Yu, Yu-cheng wrote:
> On 5/17/2021 12:45 AM, Borislav Petkov wrote:
> >On Tue, Apr 27, 2021 at 01:43:09PM -0700, Yu-cheng Yu wrote:
> >>+static inline int write_user_shstk_32(u32 __user *addr, u32 val)
> >>+{
> >>+ WARN_ONCE(1, "%s used but not supported.\n", __func__);
> >>+ return -EFAULT;
> >>+}
> >>+#endif
> >
> >What is that supposed to catch? Any concrete (mis-)use cases?
> >
>
> If 32-bit apps are not supported, there should be no need of 32-bit shadow
> stack write, otherwise there is a bug.

Speaking of which, I wonder what would happen if a 64-bit process makes
a 32-bit system call (using int 0x80, for example), and gets a signal.