Re: [PATCH 0/2] turn on force option for FUSE in builtin policies

[Mimi Zohar]

On Mon, 2018-01-15 at 09:18 -0800, Christoph Hellwig wrote:
> On Mon, Jan 15, 2018 at 11:32:41AM -0500, Mimi Zohar wrote:
> > For XFS, which considers fsmagic numbers private to the filesystem,
> > *always* using the fsmagic number is wrong. ÂAs to whether this is
> > true for other filesystems is unclear. ÂIMA policies have been defined
> > in terms of fsmagic numbers for a long time. Âfsmagic numbers were
> > moved from the filesystems to magic.h for this purpose. ÂSomeone would
> > have complained earlier if it is always wrong.
> > Â
> > I just posted a patch titled "ima: define new policy condition based
> > on the filesystem name" to allow policies to be defined in terms of
> > theÂi_sb->s_type->name.
> 
> ima has no business looking at either the name _or_ the magic number.

There are a couple of reasons to define policies in terms of the
filesystem name or magic numbers.

One example is pseudo filesystems (eg. pseudo filesystems - sysfs,
securitys, cgroups, selinuxfs, etc). ÂThese should never be measured
or appraised.

The current example is fuse and remote file systems. ÂThese should
always be re-evaluated and not rely on cached file info.

If not based on IMA policy, what do you propose? ÂDefine new SB_ flags
Âto indicate IMA disabled/enabled (eg. SB_IMA) and nocaching (eg.
SB_IMA_NOCACHE)?

Mimi