[PATCH] fs: export anon_inode_make_secure_inode() and fix secretmem LSM bypass

[Peter Zijlstra]

On Mon, Jun 23, 2025 at 04:21:15PM +0200, Vlastimil Babka wrote:
> On 6/23/25 16:01, Christoph Hellwig wrote:
> > On Mon, Jun 23, 2025 at 07:00:39AM -0700, Christoph Hellwig wrote:
> >> On Mon, Jun 23, 2025 at 12:16:27PM +0200, Christian Brauner wrote:
> >> > I'm more than happy to switch a bunch of our exports so that we only
> >> > allow them for specific modules. But for that we also need
> >> > EXPOR_SYMBOL_FOR_MODULES() so we can switch our non-gpl versions.
> >> 
> >> Huh?  Any export for a specific in-tree module (or set thereof) is
> >> by definition internals and an _GPL export if perfectly fine and
> >> expected.
> 
> Peterz tells me EXPORT_SYMBOL_GPL_FOR_MODULES() is not limited to in-tree
> modules, so external module with GPL and matching name can import.
> 
> But if we're targetting in-tree stuff like kvm, we don't need to provide a
> non-GPL variant I think?

So the purpose was to limit specific symbols to known in-tree module
users (hence GPL only).

Eg. KVM; x86 exports a fair amount of low level stuff just because KVM.
Nobody else should be touching those symbols.

If you have a pile of symbols for !GPL / out-of-tree consumers, it
doesn't really make sense to limit the export to a named set of modules,
does it?

So yes, nothing limits things to in-tree modules per-se. The
infrastructure only really cares about module names (and implicitly
trusts the OS to not overwrite existing kernel modules etc.). So you
could add an out-of-tree module name to the list (or have an out-of-free
module have a name that matches a glob; "kvm-vmware" would match "kvm-*"
for example).

But that is very much beyond the intention of things.