Messages in this thread | | | Date | Tue, 19 Mar 2013 18:02:53 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 01/12] Security: Add CAP_COMPROMISE_KERNEL |
| |
On 03/18/2013 02:32 PM, Matthew Garrett wrote: > > This means we can return our focus to the kernel. There's currently a number > of kernel interfaces that permit privileged userspace to modify the running > kernel. These are currently protected by CAP_SYS_RAWIO, but unfortunately > the semantics of this capability are poorly defined and it now covers a large > superset of the desired behaviour. >
... except it doesn't.
Looking at it in detail, EVERYTHING in CAP_SYS_RAWIO has the possibility of compromising the kernel, because they let device drivers be bypassed, which means arbitrary DMA, which means you have everything.
Now, a lot of the abuses of CAP_SYS_RAWIO have clearly been added by people who had *no bloody clue* what that capability meant, but it really doesn't change the fact that pretty much if you have CAP_SYS_RAWIO you have the machine.
So just reject CAP_SYS_RAWIO.
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
| |