[PATCH] security/ima: use fs method to read integrity data

[Christoph Hellwig]

On Wed, May 10, 2017 at 05:00:47PM -0400, Mimi Zohar wrote:
> Without i_version support the file is measured/appraised once.  With
> i_version support it will be re-measured/appraised. As a file system
> is mounted/remounted, some sort of message should be emitted
> indicating whether i_version is supported.

You can check for (sb->s_flags & MS_I_VERSION) to see if it's supported.

>  That does not imply that
> there is no value in measuring/appraising the file only once.
> 
> With this patch, the "opt-in" behavior, is only for measurement, not
> appraisal.  For appraisal, it still enforces file hash/signature
> verification, as it should, based on policy.
> 
> Christoph, could we call ->read_iter() in the NULL case as Boaz
> suggested?

No - that way you get deadlocks for every fs that uses i_rwsem in
->read_iter, which is perfectly valid behavior.

We can set ->integrity_read for every file system that's been tested
with IMA, though.  Do you have a list of known-good file systems?
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