linux-kernel - Re: [PATCH v2] ima: define ima_post_create

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Message-Id: <1548171789.4038.6.camel@linux.ibm.com>
Date:   Tue, 22 Jan 2019 10:43:09 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Goldwyn Rodrigues <rgoldwyn@...e.de>,
        Ignaz Forster <iforster@...e.de>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Fabian Vogt <fvogt@...e.de>, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2] ima: define ima_post_create_tmpfile() hook and add
 missing call

On Mon, 2019-01-21 at 14:29 +0200, Amir Goldstein wrote:
> On Mon, Jan 21, 2019 at 2:00 PM Mimi Zohar <zohar@...ux.ibm.com> wrote:
> >
> > On Thu, 2019-01-17 at 15:34 -0600, Goldwyn Rodrigues wrote:
> > > On 13:47 18/12, Mimi Zohar wrote:
> > > > If tmpfiles can be made persistent, then newly created tmpfiles need to
> > > > be treated like any other new files in policy.
> > > >
> > > > This patch indicates which newly created tmpfiles are in policy, causing
> > > > the file hash to be calculated on __fput().
> > >
> > > Discussed in overlayfs, this would be better if we use this on inode
> > > and called from vfs_tmpfile() instead of do_tmpfile(). This will cover
> > > the overlayfs case which uses tmpfiles while performing copy_up().
> > > The patch is attached.
> > >
> > > Here is the updated patch which works for my cases.
> > > However, it is the the failure case after setting the IMA flags
> > > I am concerned about, though I don't think that should be as harmful.
> >
> > Right.  The new IMA hook allocates memory for storing the flags, which
> > needs to be cleaned up on failure.  For this reason, the IMA call is
> > deferred until after the transition from locally freeing memory on
> > failure to relying on __fput().  In "do_last", the call to IMA is
> > after "opened"; and in the original version of this patch the call to
> > IMA is after finish_open().
> >
> 
> Not sure I understand the concern.
> The integrity context is associated with the inode and will be freed
> on destroy_inode() no matter which error path is taken.
> Am I missing something?

No, as long as destroy_inode() is called, it should be fine.

thanks,

Mimi