Messages in this thread | | | Date | Wed, 8 Apr 2020 09:02:57 -0700 | From | Sean Christopherson <> | Subject | Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation |
| |
On Wed, Apr 08, 2020 at 08:46:02AM -0700, Christoph Hellwig wrote: > On Wed, Apr 08, 2020 at 05:44:19PM +0200, Peter Zijlstra wrote: > > On Wed, Apr 08, 2020 at 09:27:26AM -0400, Steven Rostedt wrote: > > > On Tue, 07 Apr 2020 13:02:40 +0200 > > > Peter Zijlstra <peterz@infradead.org> wrote: > > > > > > + if (insn_is_mov_CRn(&insn) || insn_is_mov_DRn(&insn)) { > > > > + pr_err("Module writes to CRn or DRn, please use the proper accessors: %s\n", mod->name); > > > > + return -ENOEXEC; > > > > + } > > > > + > > > > > > Something like this should be done for all modules, not just out of tree > > > modules. > > > > I'm all for it; but people were worried scanning all modules was too > > expensive (I don't really believe it is, module loading just can't be a > > hot-path). Also, in-tree modules are audited a lot more than out of tree > > magic voodoo crap. > > Scanning all modules seems safer. While we're at it - can be move the > kvm bits using VMX to be always in the core kernel and just forbid > modules from using those instructions entirely?
Practically speaking, no. Turning VMX on and off (literally VMXON/VMXOFF) could be moved to helpers in the kernel, but KVM relies on inlining all post-VMXON instructions (except for VMLAUNCH/VMRESUME) for performance. VMLAUNCH/VMRESUME have their own caveats, moving them out of KVM would be messy, to say the least.
| |