[RFC PATCH v2] ima,fuse: introduce new fs flag FS_NO_IMA_CACHE

[Mimi Zohar]

On Tue, 2018-01-16 at 16:10 +0100, Alban Crequy wrote:
> From: Alban Crequy <alban at kinvolk.io>
> 
> This patch forces files to be re-measured, re-appraised and re-audited
> on file systems with the feature flag FS_NO_IMA_CACHE. In that way,
> cached integrity results won't be used.
> 
> For now, this patch adds the new flag only FUSE filesystems. This is
> needed because the userspace FUSE process can change the underlying
> files at any time.

Thanks, it's working nicely. 


> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 511fbaabf624..2bd7e73ebc2a 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2075,6 +2075,7 @@ struct file_system_type {
>  #define FS_BINARY_MOUNTDATA	2
>  #define FS_HAS_SUBTYPE		4
>  #define FS_USERNS_MOUNT		8	/* Can be mounted by userns root */
> +#define FS_NO_IMA_CACHE		16	/* Force IMA to re-measure, re-appraise, re-audit files */
>  #define FS_RENAME_DOES_D_MOVE	32768	/* FS will handle d_move() during rename() internally. */
>  	struct dentry *(*mount) (struct file_system_type *, int,
>  		       const char *, void *);
> 

Since IMA is going to need another flag, we probably should have a
consistent prefix (eg. "FS_IMA").  Maybe rename this flag to
FS_IMA_NO_CACHE.  I'm also wondering if this change should be
separated from the IMA change.

Mimi

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