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Reblogged by cstanhope@social.coop ("Your friendly 'net denizen"):

hovav@infosec.exchange ("Hovav Shacham") wrote:

We believe this bug causes the frontend to miscalculate the size of the movsb instruction, causing subsequent entries in the ROB to be associated with incorrect addresses. When this happens, the CPU enters a confused state that causes the instruction pointer to be miscalculated […]
We know that we can corrupt the system state badly enough to cause machine check errors, and we’ve also observed threads interfere with execution of processes scheduled on SMT siblings.¹

Congrats to the Googlers who found and analyzed this Intel bug,² including @taviso and @flowyroll!

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¹ https://lock.cmpxchg8b.com/reptar.html
² https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00950.html