linux-kernel - Re: [PATCH -next 0/2] lsm: Change inode

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Date:   Tue, 30 May 2023 18:01:47 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     Casey Schaufler <casey@...aufler-ca.com>
Cc:     Christoph Hellwig <hch@....de>,
        Mickaël Salaün <mic@...ikod.net>,
        Xiu Jianfeng <xiujianfeng@...wei.com>,
        gregkh@...uxfoundation.org, rafael@...nel.org,
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        wangweiyang2@...wei.com
Subject: Re: [PATCH -next 0/2] lsm: Change inode_setattr() to take struct

On Tue, May 30, 2023 at 07:55:17AM -0700, Casey Schaufler wrote:
> On 5/30/2023 7:28 AM, Christoph Hellwig wrote:
> > On Tue, May 30, 2023 at 03:58:35PM +0200, Christian Brauner wrote:
> >> The main concern which was expressed on other patchsets before is that
> >> modifying inode operations to take struct path is not the way to go.
> >> Passing struct path into individual filesystems is a clear layering
> >> violation for most inode operations, sometimes downright not feasible,
> >> and in general exposing struct vfsmount to filesystems is a hard no. At
> >> least as far as I'm concerned.
> > Agreed.  Passing struct path into random places is not how the VFS works.
> >
> >> So the best way to achieve the landlock goal might be to add new hooks
> > What is "the landlock goal", and why does it matter?
> >
> >> or not. And we keep adding new LSMs without deprecating older ones (A
> >> problem we also face in the fs layer.) and then they sit around but
> >> still need to be taken into account when doing changes.
> > Yes, I'm really worried about th amount of LSMs we have, and the weird
> > things they do.
> 
> Which LSM(s) do you think ought to be deprecated? I only see one that I

I don't have a good insight into what LSMs are actively used or are
effectively unused but I would be curious to hear what LSMs are
considered actively used/maintained from the LSM maintainer's
perspective.

> might consider a candidate. As for weird behavior, that's what LSMs are
> for, and the really weird ones proposed (e.g. pathname character set limitations)

If this is effectively saying that LSMs are licensed to step outside the
rules of the subsystem they're a guest in then it seems unlikely
subsystems will be very excited to let new LSM changes go in important
codepaths going forward. In fact this seems like a good argument against
it.