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Date:   Fri, 8 Jan 2021 19:09:35 +0100
From:   Borislav Petkov <>
To:     "Chang S. Bae" <>
Subject: Re: [PATCH v3 3/4] x86/signal: Prevent an alternate stack overflow
 before a signal delivery

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.


> 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"


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