linux-kernel - Re: [PATCH] arm64/vdso: Discard .note.gnu.property sections in vDSO

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Date:   Wed, 28 Apr 2021 18:40:10 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Bill Wendling <morbo@...gle.com>, Kees Cook <keescook@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        Daniel Kiss <Daniel.Kiss@....com>
Subject: Re: [PATCH] arm64/vdso: Discard .note.gnu.property sections in vDSO

On Wed, Apr 28, 2021 at 06:28:47PM +0100, Catalin Marinas wrote:
> On Fri, Apr 23, 2021 at 01:51:59PM -0700, Bill Wendling wrote:

> > Since the note.gnu.property section in the vDSO is not checked by the
> > dynamic linker, discard the .note.gnu.property sections in the vDSO.

> Can we not instead fix the linker script to preserve the
> .note.gnu.property, correctly aligned? It doesn't take much space and
> while we don't use it now, it has the BTI information about the binary.

> Cc'ing a few others who were involved in the BTI support.

Not just BTI, we also flag PAC usage in there too and could add other
extensions going forwards.  While the note isn't actively used by
anything right now due to the kernel mapping the vDSO prior to userspace
starting it is part of the ABI and something could end up wanting to use
it and getting confused if it's not there.  It would be much better to
fix the alignment issue.

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