linux-kernel - Re: [PATCH RFC RFT v2 2/5] fork: Add shadow stack support to clone3()

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Message-ID: <54d3bc9c-9890-49f0-9e9d-78ea4d0d7199@sirena.org.uk>
Date:   Thu, 16 Nov 2023 15:35:57 +0000
From:   Mark Brown <broonie@...nel.org>
To:     "Szabolcs.Nagy@....com" <Szabolcs.Nagy@....com>
Cc:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
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Subject: Re: [PATCH RFC RFT v2 2/5] fork: Add shadow stack support to clone3()

On Thu, Nov 16, 2023 at 01:55:07PM +0000, Szabolcs.Nagy@....com wrote:
> The 11/16/2023 12:33, Mark Brown wrote:
> > On Thu, Nov 16, 2023 at 10:32:06AM +0000, Szabolcs.Nagy@....com wrote:

> > > i guess the tricky case is stack!=0 && shadow_stack_size==0:
> > > the user may want a new shadow stack with default size logic,
> > > or (with !CLONE_VM || CLONE_VFORK) wants to use the existing
> > > shadow stack from the parent.

> > If shadow_stack_size is 0 then we're into clone() behaviour and doing
> > the default/implicit handling which is to do exactly what the above
> > describes.

> to be clear does clone with flags==CLONE_VM|CLONE_VFORK always
> use the parent shadow stack independently of the stack argument?

!CLONE_VM rather than CLONE_VM but yes, that's what the clone() and
hence current clone3() behaviour is here.

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