On 11.09.2013 09:22, Mark Tinguely wrote:
> On 09/11/13 08:55, Christoph Hellwig wrote:
> >On Tue, Sep 10, 2013 at 01:47:20PM -0500, Mark Tinguely wrote:
> >>This patch allows clients like DMF to modify an immutable file
> >>without changing the immutable capability on the file, which
> >>would expose the file to change.
> >>This patch is restricted to holders of the CAP_LINUX_IMMUTABLE,
> >>so no addition security risk has been introduced.
> >The immutable flag means that the file can't be modified, and
> >CAP_LINUX_IMMUTABLE allows setting/removing that restriction, but not
> >ignoring it.
> >So: NAK, this is a change in semantics and long-standing behaviour.
> As you said, the CAP_LINUX_IMMUTABLE allows the holder of the
> capability to turn on/off the restriction. The holder of
> CAP_LINUX_IMMUTABLE could turn off immutability, modify it and then
> turn it back on, but during that window, others could modify it too
> which may be more undesirable than changing the behavior.
It's like setting a file you own "444" only because you CAN set it to
666 doesn't mean that the check should be short-circuted.
$ touch test
$ chmod 444 test
$ echo 'Hallo' > test
-bash: test: Permission denied