Re: signal delivery, was Re: reliable reproducer

Brad Boyer
2023-04-26T21:48:46Z

On Wed, Apr 26, 2023 at 09:10:50PM +1200, Michael Schmitz wrote:
> Am 26.04.2023 um 16:42 schrieb Finn Thain:
> >If the long format frame was corrupted while on the user stack, the
> >partially completed MOVEM won't be resumed correctly. That's why I was
> >concerned about a bug in sys_sigreturn.
>
> Yes, it turns out I hadn't read mangle_kernel_stack() carefully enough. I
> thought the exception frame had remained on the kernel stack to be restored,
> but I'd missed that it is actually being restored from the user stack copy
> to the kernel stack.

Isn't that a security hole? If we restore the exception frame from
user memory, doesn't that allow a malicious program to affect the
internal state of the CPU just by handling a signal?

Brad Boyer
flar@allandria.com