On Fri, Feb 8, 2013 at 11:42 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote: > On 02/08/2013 11:18 AM, Kees Cook wrote: >> >> No. CAP_RAWIO is for reading. Writing needs a much stronger check. > > If so, I suspect we need to do this for *all* raw I/O... but I keep > wondering how much more sensitive writing really is than reading. Well, I think there's a reasonable distinction between systems that expect to strictly enforce user-space/kernel-space separation (CAP_COMPROMISE_KERNEL) and things that are fiddling with hardware (CAP_SYS_RAWIO). For example, even things like /dev/mem already have this separation (although it is stronger). You can't open /dev/mem without CAP_SYS_RAWIO, but if you do, you still can't write to RAM in /dev/mem. This might be one of the earliest examples of this distinction, actually. I think it's likely that after a while, we can convert some of these proposed CAP_COMPROMISE_KERNEL checks in always-deny once we figure out how to deal with those areas more safely. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
