Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86/fpu: verify xstate buffer size according with requested features | Date | Thu, 18 Jan 2024 23:11:40 +0100 |
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On Thu, Jan 18 2024 at 14:02, Dave Hansen wrote: > On 1/18/24 11:54, Thomas Gleixner wrote: >> On Thu, Jan 18 2024 at 10:27, Dave Hansen wrote: >>> If we have nice, reliable fault handling and then decide that we've got >>> XRSTOR's running amok reading random memory all over the place that need >>> a nicer error message, then we can add that code to predict the future. >>> If our "predict the future" code goes wrong, then we lose an error >>> message -- not a big deal. >> After staring more at it, it's arguable to pass fpstate->user_size to >> fault_in_readable() and ignore fx_sw->xstate_size completely. >> >> That's a guaranteed to be reliable size which prevents endless loops >> because arguably that's the maximum size which can be touched by XRSTOR, >> no? > > I like it. It takes fx_sw completely out of the picture, which was the > root of the problem in the first place.
Correct.
I really don't care about the esoteric case where this might theoretically result in a unjustified application abort.
You really need to twist your brain around 6 corners and then squint twice to construct that case. Of course syzcaller might trigger it, but fuzzing the sigreturn frame is a #GP, #PF and whatever lottery anyway.
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