Messages in this thread | | | From | "Edgecombe, Rick P" <> | Subject | Re: [PATCH v3 00/12] Enable Linear Address Space Separation support | Date | Tue, 1 Aug 2023 20:38:20 +0000 |
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On Tue, 2023-08-01 at 12:50 -0700, Sohil Mehta wrote: > On 7/31/2023 3:36 PM, Edgecombe, Rick P wrote: > > CET introduces this unusual instruction called WRUSS. It allows you > > to > > make user memory accesses while executing in the kernel. Because of > > this special property, the CET shadow stack patches don't toggle > > stac/clac while executing this instruction. So I think LASS will > > need > > it to behave more like a normal userspace access from the kernel. > > Shadow stack is not upstream yet, so just something to keep in mind > > for > > the future. > > > > This is a good point. We should definitely test this out to confirm. > > But, isn't WRUSS already defined as a user-mode access? So, in > theory, a > user-mode access to a user address space *should* not be blocked by > LASS > (even with CPL=0). > > Are you suggesting that we might need to do something special for > WRUSS > with LASS enabled?
I was, but reading the docs, I think you are right. It looks like it will be treated like a user access as far as LASS is concerned. Thanks.
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