Ofufuza ku ETH Zurich apanga ZenHammer attack, yosiyana ndi gulu la RowHammer la zowukira kuti lisinthe zomwe zili mumtundu wa dynamic random access memory (DRAM), zosinthidwa kuti zigwiritsidwe ntchito pamapulatifomu okhala ndi mapurosesa a AMD. Zowukira zakale za RowHammer zakhala zikugwiritsidwa ntchito ndi ma processor a Intel, koma kafukufuku wawonetsa kuti ziphuphu zamakumbukiro zitha kupezekanso pamapulatifomu okhala ndi oyang'anira kukumbukira a AMD.
Njirayi idawonetsedwa pamakina a AMD Zen 2 ndi Zen 3 okhala ndi kukumbukira kwa DDR4 kuchokera kwa opanga atatu otsogola (Samsung, Micron ndi SK Hynix). Kuwukiraku kumadutsa bwino njira ya TRR (Target Row Refresh) yomwe imayikidwa mu tchipisi ta kukumbukira, yomwe cholinga chake ndi kuteteza ku ziphuphu zama cell a kukumbukira m'mizere yoyandikana. Malinga ndi ofufuza, machitidwe ozikidwa pa AMD Zen 3 CPUs ali pachiwopsezo kwambiri kuposa machitidwe omwe ali ndi ma processor a Intel Coffee Lake, ndipo ndi osavuta komanso ogwira mtima kuukira. Pa machitidwe a AMD Zen 2, kusokonezeka kwa maselo kunatheka chifukwa cha 7 kuchokera ku 10 yoyesedwa tchipisi ta DDR4, ndi pa Zen 3 machitidwe a 6 mwa 10. Njira yopangira DDR4 idapangidwanso bwino pa 5 pa 4 yoyesedwa DDR1 tchipisi, pomwe kuthekera kowukirako sikunaphatikizidwe, koma kumafuna kupangidwa kwa njira zowerengera zomveka bwino zoyenera zida za DDR10.
Kuti agwire ntchito ndi tchipisi ta AMD, adatha kusintha zomwe zidapangidwa kale zomwe zimasintha zomwe zalembedwa patebulo latsamba lokumbukira (PTE, kulowa patebulo latsamba) kuti apeze mwayi wa kernel, kuwunika mawu achinsinsi / ulamuliro posintha kukumbukira kwa njira ya sudo. , ndikuwononga kiyi yapagulu ya RSA-2048 yosungidwa pamtima mu OpenSSH kuti mukonzenso kiyi yachinsinsi. Kuwukira kwa tsamba lokumbukira kudapangidwanso pa 7 pa tchipisi 10 za DDR4 zoyesedwa, makiyi a RSA pa tchipisi 6, ndi kuwukira kwa sudo pa tchipisi 4, ndi nthawi zowukira za 164, 267, ndi 209 masekondi, motsatana.
Njirayi ingagwiritsidwenso ntchito kuukira dongosolo kudzera pa asakatuli, kusintha makina enieni, kapena kuyambitsa kuwukira pa intaneti. Khodi yochokera pa chida cha DARE chosinthira uinjiniya wa ma adilesi mu kukumbukira kwa DRAM imayikidwa pa GitHub pansi pa laisensi ya MIT, komanso magawo awiri azinthu zoyeserera zoyeserera zachinyengo pang'ono kukumbukira - ddr4_zen2_zen3_pub ya tchipisi za DDR4 (Zen 2 ndi Zen 3) ndi ddr5_zen4_pub ya DDR5 chips (Zen 4), yomwe ingagwiritsidwe ntchito kuyesa machitidwe awo kuti ayambe kuukira.
Njira ya RowHammer imagwiritsidwa ntchito kupotoza ma bits, zomwe zimachokera ku kukumbukira kwa DRAM, komwe kuli ma cell awiri-dimensional omwe ali ndi capacitor ndi transistor, kuwerengera kosalekeza kwa dera lomwelo la kukumbukira kumabweretsa kusinthasintha kwamagetsi komanso anomalies amene amayambitsa kutayika kochepa kwa malipiro oyandikana nawo. Ngati kuchuluka kwa kuwerenga kuli kwakukulu, ndiye kuti selo loyandikana nalo likhoza kutaya ndalama zambiri zokwanira ndipo kusinthika kwina kotsatira sikudzakhala ndi nthawi yobwezeretsa chikhalidwe chake choyambirira, chomwe chidzatsogolera kusintha kwa mtengo wa deta yosungidwa mu selo. . Wofufuzayo adazindikira mawonekedwe a mapu okumbukira ndikulumikizana ndi njira zosinthira kukumbukira zomwe zimagwiritsidwa ntchito m'mapurosesa a AMD, zomwe zidapangitsa kuti zitheke kukonzanso maadiresi otsika a DRAM, kudziwa maadiresi a maselo oyandikana nawo, kupanga njira zodutsira caching, ndikuwerengera mawonekedwe ndi ma frequency. za ntchito zomwe zimabweretsa kutayika kwa mtengo.
Kuti muteteze ku RowHammer, opanga chip amagwiritsa ntchito njira ya TRR (Target Row Refresh) yomwe imaletsa ziphuphu zama cell muzochitika zapadera, koma sizimateteza kuzinthu zonse zomwe zingatheke. Njira yabwino kwambiri yodzitetezera ndiyo kugwiritsa ntchito kukumbukira ndi ma code okonza zolakwika (ECC), zomwe zimasokoneza kwambiri, koma osathetsa, kuukira kwa RowHammer. Kuwonjezeka kwafupipafupi kukumbukira kukumbukira kungathenso kuchepetsa mwayi wa kuukira kopambana.
AMD yatulutsa lipoti pankhaniyi ponena kuti mapurosesa a AMD amagwiritsa ntchito owongolera kukumbukira omwe amatsatira zomwe DDR amafotokozera, ndipo popeza kupambana kwachiwopsezo kumadalira makamaka makonda adongosolo ndi kukumbukira kwa DRAM, mafunso okhudza kuthetsa vutoli ayenera kupita kwa opanga kukumbukira. ndi machitidwe Njira zomwe zilipo zopangitsa kuti kuukira kwa gulu la Rowhammer kukhala kovuta kwambiri kumaphatikizapo kugwiritsa ntchito kukumbukira kwa ECC, kukulitsa kuchuluka kwa kukumbukira kukumbukira, kuletsa njira yosinthira yosinthidwa, komanso kugwiritsa ntchito mapurosesa okhala ndi owongolera omwe amathandizira mawonekedwe a MAC (Maximum Activate Count) a DDR4 (1st, 2nd ndi 3rd. m'badwo AMD EPYC "Naple", "Rome" ndi "Milan") ndi RFM (Refresh Management) ya DDR5 (4th generation AMD EPYC).
Source: opennet.ru