Messages in this thread | | | From | "H. Peter Anvin" <> | Subject | Re: SSE related security hole | Date | 18 Apr 2002 14:06:36 -0700 |
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Followup to: <20020418183639.20946.qmail@science.horizon.com> By author: linux@horizon.com In newsgroup: linux.dev.kernel > > Um, people here seem to be assuming that, in the absence of MMX, > fninit *doesn't* leak information. > > I thought it was well-known to just clear (set to all-ones) the > tag register and not alter the actual floating-point registers. > > Thus, it seems quite feasible to reset the tag word with FLDENV and > store out the FPU registers, even on an 80387. > > Isn't this the same security hole? Shouldn't there be 8 FLDZ instructions > (or equivalent) in the processor state initialization? >
Perhaps the right thing to do is to have a description in data of the desired initialization state and just F[NX]RSTOR it?
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