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    SubjectRe: Security fix for remapping of page 0 (was [PATCH] Change ZERO_SIZE_PTR to point at unmapped space)
    On Wed, Jun 3, 2009 at 3:42 PM, Christoph Lameter
    <> wrote:
    > On Wed, 3 Jun 2009, Eric Paris wrote:
    >> NAK  with SELinux on you now need both the SELinux mmap_zero
    >> permission and the CAP_SYS_RAWIO permission.  Previously you only
    >> needed one or the other, depending on which was the predominant
    >> LSM.....
    > CAP_SYS_RAWIO is checked so you only need to check for mmap_zero in
    > SELinux.

    You misunderstand. As it stands today if you use SELinux you need
    only the selinux mmap_zero permission. If you use capabilities you
    need CAP_SYS_RAWIO.

    With your patch SELinux policy would now have to grant CAP_SYS_RAWIO
    everywhere it grants mmap_zero. This not not acceptable. Take notice
    that with SELinux enabled cap_file_mmap is never called.....

    >> Even if you want to argue that I have to take CAP_SYS_RAWIO in the
    >> SELinux case what about all the other places?  do_mremap?  do_brk?
    >> expand_downwards?
    > brk(0) would free up all the code? The others could be added.

    The 'right'est fix is as Alan suggested, duplicate the code

    from security/capability.c::cap_file_mmap()
    to include/linux/security.h::securitry_file_mmap()

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