By: anon2 (, July 14, 2022 4:29 pm
Room: Moderated Discussions
Anon4 ( on July 14, 2022 2:17 pm wrote:
> anon2 ( on July 13, 2022 10:03 pm wrote:
> > anonymous2 ( on July 13, 2022 3:14 pm wrote:
> > >
> >
> > Does not seem to be anything new in hardware just spectre variant 2 software fix in Linux was not complete.
> Variant 2 was against forward jump instructions,

No it wasn't, it was BTB poisoning to influence indirect branches. Branch direction forwards or backwads is not relevant.

Some CPUs use BTB for return branches in some situations. This is not somehow new nor was unknown at the time. It was explicitly called out in a public discussion about the fix several years ago, actually.

> the mitigation was to turn forward jumps in to returns
> which are architecturally similar but have a very different effect on the microarchitecture.
> This was 'retpoline' retbleed attacks the retpoline itself in a similar way to
> the way variant 2 attacked jumps. It makes use of the fact that returns start behaving
> like jumps when certain internal state is overflowed. So this is novel.
> Anything which uses retpolines is vulerable and that includes
> Windows and possibly macOS it's not just a Linux issue.
> IBRS and eIRBS basically completely migitate the problem these are available from Coffee
> Lake R and beyond (Intel called it 9th gen). You will note commerical OSes have been dropping
> support for older but still relatively recent x86 processors, now you know why.

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TopicPosted ByDate
Retbleedanonymous22022/07/13 03:14 PM
  Retbleedanon22022/07/13 10:03 PM
    RetbleedAdrian2022/07/14 12:05 AM
    RetbleedAnon42022/07/14 02:17 PM
      Retbleedanon22022/07/14 04:29 PM
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              RetbleedMichael S2022/07/15 07:08 AM
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            RetbleedAnon42022/07/15 03:00 AM
          RetbleedMichael S2022/07/15 06:59 AM
      Retbleed---2022/07/15 11:14 AM
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