On Tue, May 26, 2020 at 10:17:52AM +0200, Greg KH wrote: > On Tue, May 26, 2020 at 09:57:36AM +0200, Peter Zijlstra wrote: > > On Tue, May 26, 2020 at 08:56:18AM +0200, Greg KH wrote: > > > On Mon, May 25, 2020 at 10:28:48PM -0700, Andi Kleen wrote: > > > > From: Andi Kleen <ak@xxxxxxxxxxxxxxx> > > > > > > > > Since there seem to be kernel modules floating around that set > > > > FSGSBASE incorrectly, prevent this in the CR4 pinning. Currently > > > > CR4 pinning just checks that bits are set, this also checks > > > > that the FSGSBASE bit is not set, and if it is clears it again. > > > > > > So we are trying to "protect" ourselves from broken out-of-tree kernel > > > modules now? Why stop with this type of check, why not just forbid them > > > entirely if we don't trust them? :) > > > > Oh, I have a bunch of patches pending for that :-) > > Ah, I thought I had seen something like that go by a while ago. > > It's sad that we have to write a "don't do stupid things" checker for > kernel modules now :( Because people... they get stuff from the interweb and run it :/ The days that admins actually knew what they're doing is long long gone. > > It will basically decode the module text and refuse to load the module > > for most CPL0 instruction. > > Ok, so why would Andi's patch even be needed then? Andi, why post this? Andi's patch cures a particularly bad module that floats around that people use, probably without being aware that it's an insta-root hole. My patches will be a while (too many things in the fire :/) and will certainly not be for stable.
