Messages in this thread | | | Date | Sun, 21 Apr 2002 21:52:20 +0200 | From | Pavel Machek <> | Subject | Re: SSE related security hole |
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Hi!
> > 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? > > Well, if what's on the internal stack of the FPU can actually leak > information, I think the notion of "leak" has expanded just a bit > too much. > > A rogue process could not even know what instruction was about to > be executed, nor what the previous instruction was, nor when since > boot it was executed, nor by whom. The 'data' associated with those
If fpu unit was used to memcpy your .ssh/identity, well, you might change your mind. Pavel -- (about SSSCA) "I don't say this lightly. However, I really think that the U.S. no longer is classifiable as a democracy, but rather as a plutocracy." --hpa - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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