linux-kernel - Re: [RFC PATCH v2] ima,fuse: introduce new fs flag FS_NO_IMA

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Date:   Fri, 19 Jan 2018 11:35:51 +0100
From:   Alban Crequy <alban@...volk.io>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     Alban Crequy <alban.crequy@...il.com>,
        Iago López Galeiras <iago@...volk.io>,
        Dongsu Park <dongsu@...volk.io>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Miklos Szeredi <miklos@...redi.hu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <james.l.morris@...cle.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Seth Forshee <seth.forshee@...onical.com>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [RFC PATCH v2] ima,fuse: introduce new fs flag FS_NO_IMA_CACHE

On Thu, Jan 18, 2018 at 10:25 PM, Mimi Zohar <zohar@...ux.vnet.ibm.com> wrote:
> On Tue, 2018-01-16 at 16:10 +0100, Alban Crequy wrote:
>> From: Alban Crequy <alban@...volk.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.

Ok, I can rename it.

Is there a discussion about the other IMA flag?

> I'm also wondering if this change should be
> separated from the IMA change.

Do you mean one patch for adding the flag and the IMA change and
another patch for using the flag in FUSE?

Thanks!
Alban