Messages in this thread | | | Date | Wed, 3 Jun 2009 15:51:16 -0400 | Subject | Re: Security fix for remapping of page 0 (was [PATCH] Change ZERO_SIZE_PTR to point at unmapped space) | From | Eric Paris <> |
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On Wed, Jun 3, 2009 at 3:42 PM, Christoph Lameter <cl@linux-foundation.org> 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()
-Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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