linux-kernel - Re: [PATCH 1/8] x86,kcfi: Fix EXPORT

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Message-ID: <Zyo8mdoQOXa9kiBv@infradead.org>
Date: Tue, 5 Nov 2024 07:41:13 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Christoph Hellwig <hch@...radead.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, alyssa.milburn@...el.com,
	scott.d.constable@...el.com, joao@...rdrivepizza.com,
	andrew.cooper3@...rix.com, jpoimboe@...nel.org,
	alexei.starovoitov@...il.com, ebiggers@...nel.org,
	samitolvanen@...gle.com, kees@...nel.org
Subject: Re: [PATCH 1/8] x86,kcfi: Fix EXPORT_SYMBOL vs kCFI

On Tue, Nov 05, 2024 at 03:58:42PM +0100, Peter Zijlstra wrote:
> > bounded number of functions that are used as either default methods
> > or as ready made callbacks.  Everything else has no business being
> > called indirectly.  While disallowing this might be a bit of work,
> > I think it would be a great security improvement.
> 
> Well, we don't disagree. But since most of the EXPORT'ed functions are
> done in C, we need something that works there too.

Yes, absolutely.  In fact I doubt there are more than a handful of
assembly exports that are valid targets for indirect calls.