Re: [PATCH v3 12/25] security: Introduce inode_post_setattr hook

Mimi Zohar
2023-10-12T11:44:33Z

On Thu, 2023-10-12 at 09:42 +0200, Roberto Sassu wrote:
> On Wed, 2023-10-11 at 20:08 -0400, Mimi Zohar wrote:
> > gOn Mon, 2023-09-04 at 15:34 +0200, Roberto Sassu wrote:
> > > From: Roberto Sassu <roberto.sassu@huawei.com>
> > >
> > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> > > the inode_post_setattr hook.
> > >
> > > It is useful for EVM to recalculate the HMAC on modified file attributes
> > > and other file metadata, after it verified the HMAC of current file
> > > metadata with the inode_setattr hook.
> >
> > "useful"?
> >
> > At inode_setattr hook, EVM verifies the file's existing HMAC value. At
> > inode_post_setattr, EVM re-calculates the file's HMAC based on the
> > modified file attributes and other file metadata.
> >
> > >
> > > LSMs should use the new hook instead of inode_setattr, when they need to
> > > know that the operation was done successfully (not known in inode_setattr).
> > > The new hook cannot return an error and cannot cause the operation to be
> > > reverted.
> >
> > Other LSMs could similarly update security xattrs or ...
>
> I added your sentence. The one above is to satisfy Casey's request to
> justify the addition of the new hook, and to explain why inode_setattr
> is not sufficient.

I was suggesting simplifying the wording. Perhaps something like:

Other LSMs could similarly take some action after successful file attri
bute change.

--
thanks,

Mimi