Muva nje I-AMD imemezele umsebenzi eyenzile amandla lungisa ukuba sengozini okuningi ezithinta imikhiqizo yakho. Ukuba sengozini kwakukhona kutholwe ngumcwaningi wezokuphepha uDanny Odler, okumbiko wayo odalula ukuthi amaphutha ahlala kwi-AMD Mini PC engavumela abahlaseli ukuthi basebenzise i-firmware ephephile futhi basebenzise ikhodi engaqondakali.
Lolu chungechunge lobungozi lwalukhona iqanjwe njenge- "SMM Callout" (CVE-2020-12890) kanye nokuphenywa kwezimbungulu kukhombisa ukuxhashazwa okuphelele kwe-1 kokukhubazeka okungu-3 zitholakale esithombeni se-UEFI.
Ukubizwa kwe-SMM ikuvumela ukuthi ukwazi ukulawula i-UEFI firmware futhi usebenzise ikhodi ezingeni le-SMM (Imodi yokuphathwa kwesistimu). Ukuhlaselwa kudinga ukufinyelela ngokomzimba kwikhompyutha noma ukufinyelela ohlelweni olunamalungelo okuphatha.
Uma kwenzeka kuhlaselwa ngempumelelo, umhlaseli angasebenzisa i-interface ye-AGESA (I-Generic AMD Encapsulated Software Architecture) ukwenza ikhodi engenacala ayikwazi ukutholwa kusuka kuhlelo lokusebenza.
Ubuthakathaka bukhona kukhodi efakwe ku-firmware ye-UEFI, eyenziwe ngemodi ye-SMM (Ring -2), ebaluleke kakhulu kunemodi ye-hypervisor nendandatho yokuvikela zero, futhi enokufinyelela okungenamkhawulo kuyo yonke imemori uhlelo.
Lapho ikhodi isebenza nge-SMM, yonke imemori ebonakalayo ingatholwa futhi akukho okungakuvimba ekubhaleni idatha ebucayi emakhasini womzimba we-kernel noma i-hypervisor. Ikhodi ye-SMM isebenza njengohlobo lwe-mini OS: inezinsizakalo ze-I / O, izinsizakalo zemephu yokukhumbula, ikhono lokubeka amabalazwe ezizimele, ukuphathwa kokuphazamiseka kwe-SMM, izaziso zemicimbi, nokuningi.
Ukufingqa: Ikhodi ye-SMM yikhodi enelungelo elikhulu ukwedlula yonke eyenziwe ku-CPU, ikhodi ifihlwe ngokuphelele kuhlelo lokusebenza olusebenzayo, ayikwazi ukuguqulwa yi-kernel ngisho nangamadivayisi we-DMA futhi ikhodi ebaluleke kakhulu ye-SMM ingafinyelela kunoma iyiphi imemori ebonakalayo.
Isibonelo, ngemuva kokuthola ukufinyelela ohlelweni lokusebenza njengomphumela wokuxhaphaza obunye ubungozi noma izindlela zobunjiniyela bezenhlalo, umhlaseli ingasebenzisa ubungozi ngu-SMM Callout ukudlula imodi yokuqalisa ephephile (I-UEFI Boot Ephephile), ukwethula ikhodi enonya noma i-rootkits engabonakali ohlelweni ku-SPI Flash, kanye nokuhlaselwa kwama-hypervisors we dlula izindlela zokubheka ubuqotho bezindawo ezibonakalayo.
“I-AMD iyazi ngocwaningo olusha oluhlobene nokuba sengozini okungaba khona kubuchwepheshe be-software ye-AMD enikezwe abakhiqizi bebhodi lomama ukuze bayisebenzise kwingqalasizinda yabo ye-Unified Extensible Firmware Interface (UEFI) futhi bahlela ukuqedela ukulethwa kwezinhlobo ezibuyekeziwe ezenzelwe ukunciphisa inkinga ekugcineni Juni 2020. »ifunda isimemezelo se-AMD.
“Ukuhlaselwa okuhlosiwe okuchazwe ocwaningweni kudinga ukufinyelela okuhle noma okuphathekayo kohlelo olususelwa kwi-laptop ye-AMD noma amaprosesa ashumekiwe. Uma leli zinga lokufinyelela litholakala, umhlaseli angahle asebenzise i-AMD's Generic Encapsulated Software Architecture (i-AGESA) ukwenza ikhodi engqubuzanayo ngaphandle kokutholwa uhlelo lokusebenza.
Ubuthakathaka bufanele kunephutha kwikhodi ye-SMM ngenxa ye- ngokungabikho kokuqinisekiswa kwekheli le-buffer target lapho umsebenzi weSmmGetVariable () ubizwa kusiphathi se-SMI 0xEF.
Ngenxa yale bug, umhlaseli angabhala idatha engenakuphikiswa kwimemori yangaphakathi ye-SMM (SMRAM) ayisebenzise njengekhodi elinamalungelo e-SMM. I-AMD iqaphele ukuthi ama-processor athile kuphela yethulwa phakathi kuka-2016 no-2019 bathinteka ukuba sengozini.
"I-SMM yikhodi enelungelo elikhulu kunazo zonke engasebenza ku-x86 CPU, iyivumela ukuthi ihlasele noma iyiphi ingxenye esezingeni eliphansi, kufaka phakathi iKernel neHypervisor." funda ukuhlaziywa okushicilelwe ngu-Odler.
Umthengisi we-chip usevele uhambise izinhlobo eziningi ezibuyekeziwe ze-AGESA kozakwethu. I-AMD ikhuthaza abasebenzisi ukuthi bagcine amasistimu abo esesikhathini ngokufaka ama-patches wakamuva.
Uma ufuna ukwazi kabanzi ngayo, ungaxhumana nombiko ngokuya kusixhumanisi esilandelayo.
Umthombo: https://medium.com