linux-kernel - Re: [RFC][PATCH 0/8] module: Strict per-modname namespaces

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Message-ID: <20241112092023.GL22801@noisy.programming.kicks-ass.net>
Date: Tue, 12 Nov 2024 10:20:23 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: mcgrof@...nel.org, x86@...nel.org, hpa@...or.com, petr.pavlu@...e.com,
	samitolvanen@...gle.com, da.gomez@...sung.com, masahiroy@...nel.org,
	nathan@...nel.org, nicolas@...sle.eu, linux-kernel@...r.kernel.org,
	linux-modules@...r.kernel.org, linux-kbuild@...r.kernel.org,
	hch@...radead.org, gregkh@...uxfoundation.org
Subject: Re: [RFC][PATCH 0/8] module: Strict per-modname namespaces

On Mon, Nov 11, 2024 at 04:48:58PM -0800, Sean Christopherson wrote:
> On Mon, Nov 11, 2024, Peter Zijlstra wrote:
> > Hi!
> > 
> > Implement a means for exports to be available only to an explicit list of named
> > modules. By explicitly limiting the usage of certain exports, the abuse
> > potential/risk is greatly reduced.
> > 
> > The first three 'patches' clean up the existing export namespace code along the
> > same lines of 33def8498fdd ("treewide: Convert macro and uses of __section(foo)
> > to __section("foo")") and for the same reason, it is not desired for the
> > namespace argument to be a macro expansion itself.
> > 
> > In fact, the second patch is really only a script, because sending the output
> > to the list is a giant waste of bandwidth. Whoever eventually commits this to a
> > git tree should squash these first three patches.
> > 
> > The remainder of the patches introduce the special "MODULE_<modname-list>"
> > namespace, which shall be forbidden from being explicitly imported. A module
> > that matches the simple modname-list will get an implicit import.
> > 
> > Lightly tested with something like:
> > 
> > git grep -l EXPORT_SYMBOL arch/x86/kvm/ | while read file;
> > do
> >   sed -i -e 's/EXPORT_SYMBOL_GPL(\(.[^)]*\))/EXPORT_SYMBOL_GPL_FOR(\1, "kvm,kvm-intel,kvm-amd")/g' $file;
> > done
> 
> Heh, darn modules.  This will compile just fine, but if the module contains a
> dash, loading the module will fail because scripts/Makefile.lib replaces the dash
> with an underscore the build name.  E.g. "kvm-intel" at compile time generates
> kvm-intel.ko, but the actual name of the module as seen by the kernel is kvm_intel.

I was wondering about that...  WTH is kvm doing that? I mean, I suppose
you can do: "kvm-intel,kvm_intel" but that's somewhat tedious.