linux-kernel - Re: [PATCH 3/4] integrity: IMA as an integrity service provider

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Date:	Thu, 20 Nov 2008 20:42:42 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...x-foundation.org>,
	James Morris <jmorris@...ei.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	David Safford <safford@...son.ibm.com>,
	Serge Hallyn <serue@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH 3/4] integrity: IMA as an integrity service provider

On Thu, 2008-11-20 at 13:15 -0500, Christoph Hellwig wrote: 
> Ok, after the API is sorted out I had a quick looks at this patch.
> 
> The first very odd thing is the data strucutures:
> 
> > +struct ima_args_data {
> > +	const char *filename;
> > +	struct file *file;
> > +	struct path *path;
> > +	struct dentry *dentry;
> > +	struct inode *inode;
> > +	enum lim_hooks function;
> > +	u32 osid;
> > +	int mask;
> > +};
> 
> You can always get from a file to a path, from a path to a dentry,
> from a dentry to and inode and from a path to some defintion of a
> filename.  So a lot of things here seems very redundant.
> 
> When looking at how it's used it's acually even worse.  AFAICS the
> code would be a lot cleaner if you'd just kill struct ima_args_data
> and the odd pass arguments as void pointers obsfucations and just
> pass the file/path + mask directly to the lower level functions.
> 
> That's also help killing things like ima_store_measurement which
> do entirely different things depending on idata->type.

hm, looking into it.

> > +static int skip_measurement(struct inode *inode, int mask)
> > +{
> > +	if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode))
> > +		return 1;	/* can't measure */
> > +
> > +	if (special_file(inode->i_mode) || S_ISLNK(inode->i_mode))
> > +		return 1;	/* don't measure */
> > +
> > +	if (S_ISREG(inode->i_mode))
> > +		return 0;	/* measure */
> > +	return 1;		/* don't measure */
> > +}
> 
> This could just be an
> 
> 	if (!S_ISREG(inode->i_mode))
> 
> in the caller..

Done.

> > +static int update_file_hash(struct file *f, struct path *path,
> > +			    struct hash_desc *desc)
> 
> Please split this into a update_file_hash that always operates on a
> struct file, and a wrapper around it that creates the struct file
> for the cases that needs it.

Ok.

> > +void ima_fixup_argsdata(struct ima_args_data *data, struct file *file,
> > +			struct path *path, int mask, int function)
> > +{
> > +	struct dentry *dentry = NULL;
> > +
> > +	data->file = file;
> > +	data->path = path;
> > +	data->mask = mask;
> > +	data->function = function;
> > +
> > +	if (file)
> > +		data->dentry = dentry = file->f_dentry;
> > +
> > +	if (path) {
> > +		if (!dentry)
> > +			data->dentry = dentry = path->dentry;
> > +	}
> > +	if (dentry)
> > +		data->inode = dentry->d_inode;
> > +
> > +	return;
> > +}
> 
> You have two different callers for this, either file NULL or path NULL
> but never neither or both.  So just do the setup in the callers and do
> the right thing there.  (and please kill the inode member, it's entirely
> superflous)
> 
> > +static void ima_file_free(struct file *file)
> > +{
> > +	struct inode *inode = NULL;
> > +	struct ima_iint_cache *iint;
> > +
> > +	if (!file->f_dentry)	/* can be NULL */
> > +		return;
> 
> No, it can't.
> 
> > +
> > +	inode = file->f_dentry->d_inode;
> > +	if (S_ISDIR(inode->i_mode))
> > +		return;
> > +	if ((file->f_mode & FMODE_WRITE) &&
> > +	    (atomic_read(&inode->i_writecount) == 1)) {
> 
> > + * Returns 0 on success, -ENOMEM on failure
> > + */
> > +static int ima_inode_alloc_integrity(struct inode *inode)
> > +{
> > +	return ima_iint_insert(inode);
> > +}
> > +
> > +/**
> > + * ima_inode_free_integrity - free the integrity structure
> > + * @inode: the inode structure
> > + */
> > +static void ima_inode_free_integrity(struct inode *inode)
> > +{
> > +	ima_iint_delete(inode);
> > +}
> 
> Why these wrappers?

You're right. I'll remove these routines and assign
ima_iint_insert()/delete() directly in ima_integrity_ops.

> > +	/* The file name is only a hint. */
> > +	dentry = path->dentry;
> > +	data->filename = (!dentry->d_name.name) ? (char *)dentry->d_iname :
> > +	    (char *)dentry->d_name.name;
> 
> d_iname is the internal storage for d_name, always use d_name only.

ok

> 
> > +	if (!file || !file->f_dentry)
> > +		return rc;
> 
> Can't happen.

Will remove test.

> > +#define audit_type(type) AUDIT_ ##type
> > +#define lsm_type(type) LSM_ ##type
> 
> Just spelling out the constants would be a lot more readable..

ok

Mimi

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