Re: [PATCH v5 13/21] evm: add evm_inode_post_init call in gfs2

Mimi Zohar
2011-05-16T15:51:12Z

On Mon, 2011-05-16 at 16:30 +0100, Steven Whitehouse wrote:
> Hi,
>
> On Mon, 2011-05-16 at 10:45 -0400, Mimi Zohar wrote:
> > After creating the initial LSM security extended attribute, call
> > evm_inode_post_init_security() to create the 'security.evm'
> > extended attribute.
> >
> > Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
> > ---
> > fs/gfs2/inode.c | 28 +++++++++++++++++++---------
> > 1 files changed, 19 insertions(+), 9 deletions(-)
> >
> [snip]
> > + struct xattr lsm_xattr;
> > + struct xattr evm_xattr;
> >
> > err = security_inode_init_security(&ip->i_inode, &dip->i_inode, qstr,
> > - &name, &value, &len);
> > + &lsm_xattr.name, &lsm_xattr.value,
> > + &lsm_xattr.value_len);
> >
> > if (err) {
> > if (err == -EOPNOTSUPP)
> > @@ -780,11 +781,20 @@ static int gfs2_security_init(struct gfs2_inode *dip, struct gfs2_inode *ip,
> > return err;
> > }
> >
> > - err = __gfs2_xattr_set(&ip->i_inode, name, value, len, 0,
> > - GFS2_EATYPE_SECURITY);
> > - kfree(value);
> > - kfree(name);
> > -
> > + err = __gfs2_xattr_set(&ip->i_inode, lsm_xattr.name, lsm_xattr.value,
> > + lsm_xattr.value_len, 0, GFS2_EATYPE_SECURITY);
> > + if (err < 0)
> > + goto out;
> > + err = evm_inode_post_init_security(&ip->i_inode, &lsm_xattr,
> > + &evm_xattr);
> > + if (err)
> > + goto out;
> > + err = __gfs2_xattr_set(&ip->i_inode, evm_xattr.name, evm_xattr.value,
> > + evm_xattr.value_len, 0, GFS2_EATYPE_SECURITY);
> > + kfree(evm_xattr.value);
> > +out:
> > + kfree(lsm_xattr.name);
> > + kfree(lsm_xattr.value);
> > return err;
> > }
> >
>
> Just wondering whether we could have a single call to the security
> subsystem which returns a vector of xattrs rather than having to call
> two different functions?
>
> Steve.

There are a number of places that the LSM function is called immediately
followed by either EVM/IMA. In each of those places it is hidden from
the caller by calling the security_inode_XXX_security(). In this case
each fs has it's own method of creating an extended attribute. If that
method could be passed to security_inode_init_security, then
security_inode_init_security() could call both the LSM and EVM functions
directly.

Mimi