linux-kernel - Re: [PATCH v2] fsnotify, lsm: Decouple fsnotify from lsm

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Message-ID: <20241014153802.bgimwlm37mqbf5m4@quack3>
Date: Mon, 14 Oct 2024 17:38:02 +0200
From: Jan Kara <jack@...e.cz>
To: Amir Goldstein <amir73il@...il.com>
Cc: Song Liu <songliubraving@...a.com>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Song Liu <song@...nel.org>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	LSM List <linux-security-module@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>, Paul Moore <paul@...l-moore.com>,
	James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Kernel Team <kernel-team@...a.com>
Subject: Re: [PATCH v2] fsnotify, lsm: Decouple fsnotify from lsm

On Sun 13-10-24 16:51:35, Amir Goldstein wrote:
> On Sun, Oct 13, 2024 at 4:46 PM Song Liu <songliubraving@...a.com> wrote:
> >
> > Hi Amir,
> >
> > > On Oct 13, 2024, at 2:38 AM, Amir Goldstein <amir73il@...il.com> wrote:
> > >
> > > On Sun, Oct 13, 2024 at 2:23 AM Song Liu <song@...nel.org> wrote:
> > >>
> > >> Currently, fsnotify_open_perm() is called from security_file_open(). This
> > >> is not right for CONFIG_SECURITY=n and CONFIG_FSNOTIFY=y case, as
> > >> security_file_open() in this combination will be a no-op and not call
> > >> fsnotify_open_perm(). Fix this by calling fsnotify_open_perm() directly.
> > >
> > > Maybe I am missing something.
> > > I like cleaner interfaces, but if it is a report of a problem then
> > > I do not understand what the problem is.
> > > IOW, what does "This is not right" mean?
> >
> > With existing code, CONFIG_FANOTIFY_ACCESS_PERMISSIONS depends on
> > CONFIG_SECURITY, but CONFIG_FSNOTIFY does not depend on
> > CONFIG_SECURITY. So CONFIG_SECURITY=n and CONFIG_FSNOTIFY=y is a
> > valid combination. fsnotify_open_perm() is an fsnotify API, so I
> > think it is not right to skip the API call for this config.
> >
> > >
> > >>
> > >> After this, CONFIG_FANOTIFY_ACCESS_PERMISSIONS does not require
> > >> CONFIG_SECURITY any more. Remove the dependency in the config.
> > >>
> > >> Signed-off-by: Song Liu <song@...nel.org>
> > >> Acked-by: Paul Moore <paul@...l-moore.com>
> > >>
> > >> ---
> > >>
> > >> v1: https://lore.kernel.org/linux-fsdevel/20241011203722.3749850-1-song@kernel.org/
> > >>
> > >> As far as I can tell, it is necessary to back port this to stable. Because
> > >> CONFIG_FANOTIFY_ACCESS_PERMISSIONS is the only user of fsnotify_open_perm,
> > >> and CONFIG_FANOTIFY_ACCESS_PERMISSIONS depends on CONFIG_SECURITY.
> > >> Therefore, the following tags are not necessary. But I include here as
> > >> these are discussed in v1.
> > >
> > > I did not understand why you claim that the tags are or not necessary.
> > > The dependency is due to removal of the fsnotify.h include.
> >
> > I think the Fixes tag is also not necessary, not just the two
> > Depends-on tags. This is because while fsnotify_open_perm() is a
> > fsnotify API, only CONFIG_FANOTIFY_ACCESS_PERMISSIONS really uses
> > (if I understand correctly).
> >
> 
> That is correct.
> 
> > >
> > > Anyway, I don't think it is critical to backport this fix.
> > > The dependencies would probably fail to apply cleanly to older kernels,
> > > so unless somebody cares, it would stay this way.
> >
> > I agree it is not critical to back port this fix. I put the
> > Fixes tag below "---" for this reason.
> >
> > Does this answer your question?
> >
> 
> Yes, I agree with not including any of the tags and not targeting stable.
> 
> Jan, Christian,
> 
> do you agree with the wording of the commit message, or think
> that it needs to be clarified?
> 
> Would you prefer this to go via the fsnotify tree or vfs tree?

I guess I'll take this through fsnotify tree after updating the changelog a
bit.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR