Mva nje Iqela labaphandi abavela kwiYunivesithi yaseGraz yeTekhnoloji (Ostriya) kunye neZiko leHelmholtz loKhuseleko loLwazi (CISPA) ikhuphe ulwazi malunga nokuba sesichengeni (I-CVE-2021-26318) kuzo zonke iiprosesa ze-AMD enokuvumela iMeltdown-class uhlaselo lwetshaneli esecaleni.
Ujongene nolwazi oluveziweyo lomntu lwe I-AMD yenze kwaziwa ukuba ikubona kungafanelekanga ukuthatha amanyathelo akhethekileyo ukuvimba ingxaki, ekubeni ubuthathaka, njengohlaselo olufanayo olufunyenwe ngo-Agasti, alusebenzi kangako kwiimeko zokwenyani, kuba ikhankanya ukuba ilinganiselwe yimida yangoku yendawo yedilesi yenkqubo kwaye ifuna ulandelelwano lwemiyalelo (igajethi) kwi-kernel. Ukubonisa uhlaselo, abaphandi balayishe imodyuli yabo yekernel ngesixhobo esongeziweyo. Kubomi bokwenene, abahlaseli banokuthi, umzekelo, basebenzise rhoqo ubuthathaka kwi-subsystem ye-EBPF ukubuyisela ukulandelelana okuyimfuneko.
Ukusuka kwindawo ebonakalayo, uhlaselo lungasetyenziselwa ukuququzelela amajelo osasazo edatha efihlakeleyo, ukubeka iliso kumsebenzi kwi-kernel okanye ufumane ulwazi malunga needilesi kwimemori ye-kernel ukuphepha ukhuseleko olusekwe kwi-randomization yeedilesi (KASLR) kwinkqubo yokuxhaphaza ubuthathaka kwi-kernel.
Sifumene ixesha kunye nokwahluka kwamandla omyalelo wokulanda kwangaphambili onokuthi uqwalaselwe kwindawo yomsebenzisi engenalo ilungelo. Ngokungafaniyo nomsebenzi wangaphambili kuhlaselo lwangaphambili e-Intel, sibonise ukuba umyalelo wokulanda kwangaphambili kwi-AMD uhluza ulwazi oluninzi. Sibonisa ukubaluleka kweli jelo lecala kunye nezifundo ezininzi kwiimeko zehlabathi lokwenyani. Sibonisa ukuwohloka kokuqala kwe-KASLR microarchitecture.
Ukuzikhusela kolu hlaselo lutsha, i-AMD indulule ukusetyenziswa kobuchule bokubhala obukhuselekileyo enceda ukuthintela uhlaselo lwe-Meltdown, njengokusebenzisa iingxelo zeLFENCE. Abaphandi abachonge umba bacebisa ukuba kuvumeleke ukwahlulwa kwetafile yememori engqongqo (KPTI), ebifudula isetyenziselwa abaqhubekekisi be-Intel.
Ngexesha lovavanyo, abaphandi bakwazile ukuvuza ulwazi kwi-kernel ukuya kwinkqubo kwindawo yomsebenzisi.okanye ngesantya se-52 bytes ngomzuzwana, ukuba kukho isixhobo kwi-kernel esenza umsebenzi, iindlela ezininzi ziye zacetywa ukukhupha ulwazi olugcinwe kwi-cache ngexesha lokubulawa okuqikelelwayo ngokusebenzisa iziteshi zomntu wesithathu.
Indlela yokuqala isekelwe kuhlalutyo lokuphambuka kwexesha lokubulawan yomyalelo weprosesa kunye neyesibini yokutshintsha kwinguqu yokusetyenziswa kwamandla xa "PREFETCH" (Prefetch + Power) isenziwa.
Sibeka esweni umsebenzi we-kernel, umzekelo ukuba i-audio idlalwa ngeBluetooth, kwaye siseka itshaneli efihlakeleyo. Okokugqibela, siye sahluza imemori ye-kernel kwi-52.85 B / s ngezixhobo ezilula zeSpecter kwi-Linux kernel. Sibonisa ukuba ukwahlulwa kwetafile eyomeleleyo kufuneka kwenziwe kwii-AMD CPU ngokungagqibekanga ukunciphisa uhlaselo lwethu olungeniswe ngempumelelo
Khumbula ukuba sesichengeni se-Meltdown sakudala sisekwe into yokuba ngexesha uphumezo oluqikelelwayo lwemiyalelo umqhubekekisi unokufikelela kwindawo yedatha yabucala kwaye alahle isiphumo, kuba amalungelo asekiweyo athintela ufikelelo olunjalo kwinkqubo yomsebenzisi. Kwiprogram, ibhloko eyenziwe ngokuqikelelwayo ihlukaniswe kwikhowudi ephambili yisebe elinemiqathango, phantsi kweemeko zangempela lihlala liqhutywe, kodwa ngenxa yokuba isibhengezo esinemiqathango sisebenzisa ixabiso elibaliweyo ukuba iprosesa engayazi ngexesha lokwenziwa kwekhowudi yokuqala. , ukuphunyezwa okuqikelelwayo kwazo zonke iinketho zamasebe ziyenziwa.
Ekubeni imisebenzi eqikelelwayo isebenzisa i-cache efanayo kunemiyalelo eqhelekileyo eyenziwa, kuyenzeka ngexesha lofezekiso oluqikelelwayo kwiziphawuli ze-cache ezibonisa umxholo webit iifayile zomntu ngamnye kwindawo yememori evaliweyo, kwaye emva koko kwikhowudi edlalwa ngokuqhelekileyo ukumisela ixabiso labo ngokuhlalutya ixesha lifikelela kuzo zombini idatha egciniweyo kunye ne-non-cached.
Gqibela ukuba unomdla wokwazi okungakumbi ngayo, ungajonga iinkcukacha Kule khonkco ilandelayo.