On Fri, Aug 07, 2015 at 10:32:57AM -0400, Josh Boyer wrote: > On Fri, Aug 07, 2015 at 09:09:43AM -0400, Vivek Goyal wrote: > > On Fri, Aug 07, 2015 at 07:15:57AM -0400, Josh Boyer wrote: > > > On Fri, Aug 7, 2015 at 3:41 AM, Dave Young <dyoung@xxxxxxxxxx> wrote: > > > > Kexec reboot in case secure boot enabled does not keep the secure boot mode > > > > in new kernel, so later one can load unsigned kernel via legacy kexec_load. > > > > > > Hm. Wasn't there code being written so that one could disable legacy > > > kexec and only have kexec_file? Perhaps that is queued for 4.3. I'm > > > wondering if as a general security measure we want to only have > > > kexec_file available in Fedora when that is possible. > > > > The way config options are in fedora, kexec_file() enforces signature > > verification. So if you disable legacy kexec, then it will not be possible > > to kexec unsigned kernels. > > Yes, which is what I was thinking we would want. However, I suppose > people might still wish to build and kexec unsigned kernels on non-SB > machines so that's probably not the right choice. Bummer. > > > I think we should be able to modify kexec_file() such that it enfornces > > signature only when secureboot is enabled otherwise acts like a legacy > > call. Then we should be able to get rid of legacy kexec call. > > Right, but then we'd still have to carry Dave's patch because it will > run into the same issue legacy kexec has today. Right. I think Dave's patch is required anyway. > > > But there is a long way to go before we get there. legacy call is well > > tested and new call is barely used anywhere. First we need to have > > confidence that new call can handle most of the use cases. > > Out of curiosity, does kexec-tools use the new system call by default? > I suppose that would be one way to get it tested in a broad manner. Right now kexec-tools switch to new call only if machine is secureboot enabled. Otherwise they default to old call. I think first somebody needs to audit kexec-tools code and see if all major features we suppor there are available in new call or not. And then one can think of switching default in kexec-tools. Thanks Vivek _______________________________________________ kernel mailing list kernel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/kernel
