On Sun, Sep 24, 2017 at 12:59:06PM +0200, Ingo Molnar wrote:
> @@ -328,10 +331,8 @@ static int __fpu__restore_sig(void __user *buf, void
> __user *buf_fx, int size)
> err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
> } else {
> err = __copy_from_user(&fpu->state.xsave, buf_fx,
> state_size);
> -
> - /* xcomp_bv must be 0 when using uncompacted format */
> - if (!err && fpu->state.xsave.header.xcomp_bv)
> - err = -EINVAL;
> + if (!err)
> + err =
> validate_xstate_header(&fpu->state.xsave.header);
> }
>
Sorry, this is the buggy part. The problem is that this code runs even if XSAVE
isn't being used --- and in that case the state size is 512 bytes or less, so
the state doesn't actually include the xstate_header. So
validate_xstate_header() was reading out of bounds and seeing invalid values.
So I think we need to check use_xsave() here, but it really needs to be in the
earlier patch which added the check for just ->xcomp_bv ("x86/fpu: Don't let
userspace set bogus xcomp_bv"), not in this one.
As far the split of patch 2/3 into these 10 patches, it looks fine (though it
suddenly became a *lot* of patches!). One nit: the subject of this one really
should say "__fpu__restore_sig()", not "sanitize_restored_xstate()".
I can send a fixed series when I have a chance.
Eric
