linux-kernel - Re: [PATCH 0/2] ima: add dont_audit and fs

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Message-ID: <CAG48ez1jqa2y=aTJ=C+s9v0_xhWra7gezdY+BO=Red-XVGNQJQ@mail.gmail.com>
Date: Tue, 30 Sep 2025 16:26:28 +0200
From: Jann Horn <jannh@...gle.com>
To: Mimi Zohar <zohar@...ux.ibm.com>
Cc: Roberto Sassu <roberto.sassu@...wei.com>, Dmitry Kasatkin <dmitry.kasatkin@...il.com>, 
	Eric Snowberg <eric.snowberg@...cle.com>, Frank Dinoff <fdinoff@...gle.com>, 
	linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org
Subject: Re: [PATCH 0/2] ima: add dont_audit and fs_subtype to policy language

On Tue, Sep 30, 2025 at 12:23 PM Mimi Zohar <zohar@...ux.ibm.com> wrote:
> On Fri, 2025-09-26 at 01:45 +0200, Jann Horn wrote:
> > This series adds a "dont_audit" action that cancels out following
> > "audit" actions (as we already have for other action types), and also
> > adds an "fs_subtype" that can be used to distinguish between FUSE
> > filesystems.
> >
> > With these two patches applied, as a toy example, you can use the
> > following policy:
> > ```
> > dont_audit fsname=fuse fs_subtype=sshfs
> > audit func=BPRM_CHECK fsname=fuse
> > ```
> >
> > I have tested that with this policy, executing a binary from a
> > "fuse-zip" FUSE filesystem results in an audit log entry:
> > ```
> > type=INTEGRITY_RULE msg=audit([...]): file="/home/user/ima/zipmount/usr/bin/echo" hash="sha256:1d82e8[...]
> > ```
> > while executing a binary from an "sshfs" FUSE filesystem does not
> > generate any audit log entries.
> >
> > Signed-off-by: Jann Horn <jannh@...gle.com>
>
>
> Thanks, Jann.  The patches look fine.  Assuming the "toy" test program creates
> and mounts the fuse filesystems, not just loads the IMA policy rules, could you
> share it?

Thanks for the quick review! To clarify, by "toy example" I meant that
while I was using real FUSE filesystems, the policy I was using is not
very sensible.

I used real FUSE filesystems for this since I figured that would be
the easiest way to test, https://github.com/libfuse/sshfs and
https://bitbucket.org/agalanin/fuse-zip. These are packaged in distros
like Debian (as "sshfs" and "fuse-zip"). I mounted sshfs with these
commands (mounting the home directory over ssh at ~/mnt/ssh):

user@vm:~$ cp /usr/bin/echo ~/ima/
user@vm:~$ sshfs localhost: ~/mnt/ssh

and mounted fuse-zip with:

user@vm:~/ima$ zip -rD echo.zip /usr/bin/echo
  adding: usr/bin/echo (deflated 62%)
user@vm:~/ima$ mkdir zipmount
user@vm:~/ima$ fuse-zip echo.zip zipmount/

I then ran the executables ~/ima/zipmount/usr/bin/echo and ~/mnt/ssh/ima/echo.