Re: [PATCH v3 3/4] x86/signal: Prevent an alternate stack overflow before a signal delivery

Borislav Petkov
2021-01-08T18:10:41Z

On Tue, Dec 22, 2020 at 05:53:11PM -0800, Chang S. Bae wrote:
> The kernel pushes data on the userspace stack when entering a signal. If
> using a sigaltstack(), the kernel precisely knows the user stack size.
^^^^^^^^^^^^^^^^^^^^^^^

Formulate properly.

>
> When the kernel knows that the user stack is too small, avoid the overflow
> and do an immediate SIGSEGV instead.
^^^^^^^^^^^^^^^^^^^^^^^

Ditto.

> This overflow is known to occur on systems with large XSAVE state. The
> effort to increase the size typically used for altstacks reduces the
^^^^^^^^^^

"alternate signal stacks"

--
Regards/Gruss,
Boris.

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