Analogy fail. The /dev/mem lockout applies to system RAM, not MMIO. I fear COMPROMISE_KERNEL is becoming the new SYS_ADMIN, which in turn is the new root. Why? Because it is inhebtly about a usage model, not about a specific resource. Kees Cook <keescook@xxxxxxxxxxxx> wrote: >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 -- Sent from my mobile phone. Please excuse brevity and lack of formatting. -- 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
