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    SubjectRe: [PATCH -v3 1/3] Capabilities: move cap_file_mmap to commoncap.c
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    On Thu, 2009-07-30 at 13:50 -0400, Eric Paris wrote:
    > On Thu, 2009-07-30 at 11:58 -0400, Stephen Smalley wrote:
    > > On Thu, 2009-07-30 at 10:54 -0500, Serge E. Hallyn wrote:
    > > > Quoting Eric Paris (eparis@redhat.com):
    > > > > On Thu, 2009-07-30 at 00:14 -0500, Serge E. Hallyn wrote:
    > > > > > Quoting Eric Paris (eparis@redhat.com):
    > > > > > > Currently we duplicate the mmap_min_addr test in cap_file_mmap and in
    > > > > > > security_file_mmap if !CONFIG_SECURITY. This patch moves cap_file_mmap
    > > > > > > into commoncap.c and then calls that function directly from
    > > > > > > security_file_mmap ifndef CONFIG_SECURITY like all of the other capability
    > > > > > > checks are done.
    > > > > >
    > > > > > It also
    > > > > >
    > > > > > 1. changes the return value in error case from -EACCES to
    > > > > > -EPERM
    > > > > > 2. no onger sets PF_SUPERPRIV in t->flags if the capability
    > > > > > is used.
    > > > > >
    > > > > > Do we care about these?
    > > > >
    > > > > Personally, not really, but I'll gladly put them back if you care. #2
    > > > > seems more interesting to me than number 1. I actually kinda like
    > > > > getting EPERM from caps rather than EACCES since them I know if I was
    > > > > denied by selinux or by caps.....
    > > > >
    > > > > -Eric
    > > >
    > > > Yup, I asked bc I didn't particularly care myself.
    > > >
    > > > I think I agree with you about -EPERM being better anyway. However I
    > > > (now) think in this case PF_SUPERPRIV definately should be set, as this
    > > > is a clear use of a capability to do something that couldn't have been
    > > > done without it.
    > >
    > > On a related but different note, we should consider all current uses of
    > > cap_capable(), as they represent capability checks that will not be
    > > subject to a further restrictive check by other security modules. In
    > > this case and in the vm_enough_memory case, that is intentional, but not
    > > so clear for other uses in commoncap.c.
    >
    > Most of commoncap.c is called either as a secondary hook from the active
    > lsm (aka selinux calls the commoncap.c functions) or in the !
    > CONFIG_SECURITY case.
    >
    > I'll audit this afternoon to see which of them might not fit these
    > rules....

    I just went through all of the cap_* function in commoncap.c to see
    which of them are being or are not being called from the selinux hooks.
    Only 3 of them look interesting.

    cap_inode_setxattr
    cap_inode_removexattr
    cap_vm_enough_memory

    All of the other functions are either called from hooks.c or SELinux
    does not define that LSM hook, so it just defaults to the cap_* hook.

    These 3 are all a bit odd because the logic inside the cap_ hook is
    duplicated inside the selinux_ hook. I'd much rather see the selinux_
    hook call the cap_ hook. I'm going to think on that topic, but it's a
    different set of patches and I don't see missing checks today as the
    logic seems to line up.

    -Eric



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