linux-kernel - Re: [PATCH 00/35] Shadow stacks for userspace

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Message-ID: <Yf/Hy+MknkkmyLi/@hirez.programming.kicks-ass.net>
Date:   Sun, 6 Feb 2022 14:06:19 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH 00/35] Shadow stacks for userspace

On Fri, Feb 04, 2022 at 01:08:25AM +0000, Edgecombe, Rick P wrote:

> > So how is that going to work? altstack is not an esoteric corner
> > case.
> 
> My understanding is that the main usages for the signal stack were
> handling stack overflows and corruption. Since the shadow stack only
> contains return addresses rather than large stack allocations, and is
> not generally writable or pivotable, I thought there was a good
> possibility an alt shadow stack would not end up being especially
> useful. Does it seem like reasonable guesswork?

altstacks are also used in userspace threading implemenations.