linux-kernel - Re: [PATCH v5 2/7] lsm: introduce new hooks for setting/getting inode fsxattr

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Message-ID: <kgl5h2iruqnhmad65sonlvneu6mdj6jl3sd4aoc3us3lvrgviy@imce27t4nk2e>
Date: Wed, 14 May 2025 13:02:13 +0200
From: Andrey Albershteyn <aalbersh@...hat.com>
To: Casey Schaufler <casey@...aufler-ca.com>
Cc: Richard Henderson <richard.henderson@...aro.org>, 
	Matt Turner <mattst88@...il.com>, Russell King <linux@...linux.org.uk>, 
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	linux-xfs@...r.kernel.org, Andrey Albershteyn <aalbersh@...nel.org>
Subject: Re: [PATCH v5 2/7] lsm: introduce new hooks for setting/getting
 inode fsxattr

On 2025-05-12 08:43:32, Casey Schaufler wrote:
> On 5/12/2025 6:25 AM, Andrey Albershteyn wrote:
> > Introduce new hooks for setting and getting filesystem extended
> > attributes on inode (FS_IOC_FSGETXATTR).
> >
> > Cc: selinux@...r.kernel.org
> > Cc: Paul Moore <paul@...l-moore.com>
> >
> > Signed-off-by: Andrey Albershteyn <aalbersh@...nel.org>
> > ---
> >  fs/file_attr.c                | 19 ++++++++++++++++---
> >  include/linux/lsm_hook_defs.h |  2 ++
> >  include/linux/security.h      | 16 ++++++++++++++++
> >  security/security.c           | 30 ++++++++++++++++++++++++++++++
> >  4 files changed, 64 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/file_attr.c b/fs/file_attr.c
> > index 2910b7047721..be62d97cc444 100644
> > --- a/fs/file_attr.c
> > +++ b/fs/file_attr.c
> > @@ -76,10 +76,15 @@ EXPORT_SYMBOL(fileattr_fill_flags);
> >  int vfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
> >  {
> >  	struct inode *inode = d_inode(dentry);
> > +	int error;
> >  
> >  	if (!inode->i_op->fileattr_get)
> >  		return -ENOIOCTLCMD;
> >  
> > +	error = security_inode_file_getattr(dentry, fa);
> > +	if (error)
> > +		return error;
> > +
> 
> If you're changing VFS behavior to depend on LSMs supporting the new
> hooks I'm concerned about the impact it will have on the LSMs that you
> haven't supplied hooks for. Have you tested these changes with anything
> besides SELinux?

Sorry, this thread is incomplete, I've resent full patchset again.
If you have any further comments please comment in that thread [1]

I haven't tested with anything except SELinux, but I suppose if
module won't register any hooks, then security_inode_file_*() will
return 0. Reverting SELinux implementation of the hooks doesn't
cause any errors.

I'm not that familiar with LSMs/selinux and its codebase, if you can
recommend what need to be tested while adding new hooks, I will try
to do that for next revision.

[1]: https://lore.kernel.org/linux-fsdevel/CAOQ4uxgOAxg7N1OUJfb1KMp7oWOfN=KV9Lzz6ZrX0=XRGOQrEQ@mail.gmail.com/T/#t

-- 
- Andrey