On 02/27/2014 02:34 PM, Daniel J Walsh wrote: > On 02/27/2014 02:25 PM, Paul Moore wrote: >> On Thursday, February 27, 2014 11:26:35 AM Stephen Smalley wrote: >>> On 02/27/2014 11:22 AM, Paul Moore wrote: >>>> On Thursday, February 27, 2014 10:57:46 AM Stephen Smalley wrote: >>>>> On 02/27/2014 09:30 AM, Paul Moore wrote: >>>>>> It turns out that doing the SELinux MAC checks for mmap() before >>>>>> the DAC checks was causing users and the SELinux policy folks >>>>>> headaches as users were seeing a lot of SELinux AVC denials for >>>>>> the memprotect:mmap_zero permission that would have also been >>>>>> denied by the normal DAC capability checks (CAP_SYS_RAWIO). >>>>> >>>>> So you think that the explanation given in the comment for the >>>>> current ordering is no longer valid? >>>> >>>> Yes and no. Arguably there is still some value in it but there are >>>> enough problems with it as-is that I think the value is starting to be >>>> outweighed by the pain it is causing (Dan can be very annoying when he >>>> wants something <g>). For those users who still want notification of >>>> processes trying to mmap() low addresses, I think an audit watch is a >>>> much better approach. I don't think SELinux shouldn't be acting as an >>>> intrustion detection tool when we have other things that do that job. >>>> >>>> Let's also not forget that the MAC-before-DAC approach goes against >>>> the general approach to applying SELinux controls, so there is some >>>> argument to be had for consistency as well. >>>> >>>> Do you have a strong objection to this patch? >>> >>> No, although I do wonder if we ought to just dispense with mmap_zero >>> altogether at this point. It made sense when there was no capability >>> check or if the capability was one of the extremely broad ones (e.g. >>> CAP_SYS_ADMIN), but I don't really see why we can't be just as >>> restrictive with CAP_SYS_RAWIO / sys_rawio as with mmap_zero. > >> Seems like a reasonable argument to me. I pinged Eric to get his thoughts >> on the issue since he added the check originally; if he is okay with >> removing it, I'll go ahead do it. > > The only thing is this is a nice debugging tool for the kernel. Finding apps > that accidentally mmap_zero. You'll still see sys_rawio avc denials and the audit syscall record will show that it was mmap of a low address. _______________________________________________ Selinux mailing list Selinux@xxxxxxxxxxxxx To unsubscribe, send email to Selinux-leave@xxxxxxxxxxxxx. To get help, send an email containing "help" to Selinux-request@xxxxxxxxxxxxx.
