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    SubjectRe: [PATCH 3/3] CRED: Move the effective capabilities into the cred struct

    --- Trond Myklebust <> wrote:

    > On Wed, 2007-09-19 at 21:11 -0700, Andrew Morgan wrote:
    > > -----BEGIN PGP SIGNED MESSAGE-----
    > > Hash: SHA1
    > >
    > > David Howells wrote:
    > > > Move the effective capabilities mask from the task struct into the
    > credentials
    > > > record.
    > > >
    > > > Note that the effective capabilities mask in the cred struct shadows that
    > in
    > > > the task_struct because a thread can have its capabilities masks changed
    > by
    > > > another thread. The shadowing is performed by update_current_cred()
    > which is
    > > > invoked on entry to any system call that might need it.
    > >
    > > OOC If we were to simply drop support for one process changing the
    > > capabilities of another, would we need this patch?
    > No. This has nothing to do about one process changing some other
    > process' capabilities. It has to do with being able to pass security
    > information around the kernel beyond the confines of the task struct.
    > This is needed in order to deal with asynchronous i/o where security
    > checks may have to be deferred, and where the task struct may no longer
    > be available.
    > One example would be a failover situation when doing deferred writes: if
    > the first choice of storage medium is unavailable, and the kernel tries
    > to fail the write over to another storage. On NFS that might involve
    > having to build up a new RPCSEC_GSS security context for the new server.
    > Currently, you cannot do this safely because all the security info is
    > cached in the task struct and much of it cannot be copied.

    Ok, what can't be copied, and why can't it be copied?

    Casey Schaufler
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      Last update: 2007-09-20 17:39    [W:0.020 / U:8.012 seconds]
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