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    SubjectRe: [PATCH v5 13/21] evm: add evm_inode_post_init call in gfs2
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    Hi,

    On Wed, 2011-05-18 at 20:55 -0400, Mimi Zohar wrote:
    > On Mon, 2011-05-16 at 12:25 -0700, Casey Schaufler wrote:
    > > On 5/16/2011 11:48 AM, Mimi Zohar wrote:
    > > > On Mon, 2011-05-16 at 11:23 -0700, Casey Schaufler wrote:
    >
    > > >> There is a very real possibility that multiple concurrent LSMs will
    > > >> be supported before too long. Smack already uses multiple attributes
    > > >> (SMACK64, SMACK64EXEC) on a file. Getting all the attributes in a
    > > >> single call could result in an interface that requires parsing a
    > > >> string argument, and we all know how popular those are. Introducing
    > > >> an interface that we know isn't going to accommodate this upcoming
    > > >> direction does not seem prudent.
    > > > I would think that Smack would benefit from Steven's suggestion of
    > > > returning an array of xattrs. Without his suggestion, I'm not sure how
    > > > you are, or planning on, initializing multiple xattrs from a single LSM,
    > > > unless of course you're not using security_inode_init_security().
    > >
    > > The good news is that Smack has one required attribute. The others
    > > are for special purposes and will usually be absent. It is easy to
    > > imagine an LSM that always uses multiple attributes on a given file.
    > >
    > > Yes, the array of xattr structures makes sense for any one LSM,
    > > but there still needs to be the potential for multiple calls for
    > > the multiple LSM case. I can't see that going away without a radical
    > > LSM restructuring.
    > >
    > > > Multiple LSMs calling security_inode_init_security() will be an issue
    > > > for EVM, as EVM assumes there is a single LSM xattr on which to base the
    > > > initial hmac.
    > >
    > > That is far from the biggest issue with multiple LSMs, but is definitely
    > > something to worry about.
    >
    > Ok. After thinking about this a bit more, moving
    > evm_inode_init_security() into security_inode_init_security() only works
    > for the single LSM and EVM case, but not for the multiple LSMs and EVM
    > case, as the 'stacker' would call each LSM's
    > security_inode_iint_security(). Having the 'stacker' return an array of
    > xattrs would make sense and, at the same time, resolve the EVM issue. In
    > evm_inode_post_init_security(), EVM could then walk the list of xattrs.
    >
    > Mimi
    >
    >
    >
    That sounds like a reasonable solution to me,

    Steve.




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