Messages in this thread | | | Date | Tue, 7 Apr 2020 11:49:32 -0700 | From | Kees Cook <> | Subject | Re: [PATCH 4/4] x86,module: Detect CRn and DRn manipulation |
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On Tue, Apr 07, 2020 at 08:13:25PM +0200, Peter Zijlstra wrote: > On Tue, Apr 07, 2020 at 10:01:04AM -0700, Kees Cook wrote: > > On Tue, Apr 07, 2020 at 01:02:40PM +0200, Peter Zijlstra wrote: > > > Since we now have infrastructure to analyze module text, disallow > > > modules that write to CRn and DRn registers. > > > > > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > > --- > > > arch/x86/kernel/module.c | 21 +++++++++++++++++++++ > > > 1 file changed, 21 insertions(+) > > > > > > --- a/arch/x86/kernel/module.c > > > +++ b/arch/x86/kernel/module.c > > > @@ -266,6 +266,22 @@ static bool insn_is_vmx(struct insn *ins > > > return false; > > > } > > > > > > +static bool insn_is_mov_CRn(struct insn *insn) > > > +{ > > > + if (insn->opcode.bytes[0] == 0x0f && insn->opcode.bytes[1] == 0x22) > > > + return true; > > > > I always cringe at numeric literals. Would it be overkill to add defines > > for these (and the others that have comments next to them in 3/4)? It > > makes stuff easier to grep, etc. (e.g. we have register names in > > arch/x86/include/asm/asm.h, do we need instruction names somewhere else? > > I assume objtool has a bunch of this too...) > > objtool does not, have a peek at tools/objtool/arch/x86/decode.c
Eek.
> I'm not sure what the best way is here, the x86 opcode map is a > disaster. Even the mnemonic doesn't help us here, as that's just MOV :/
Yeah, I'm not sure either. I guess leave this as-is.
-- Kees Cook
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