Ukuba sesichengeni kweGhostRace
Ulwazi malunga a uhlaselo olutsha oluqikelelwayo, olubizwa ngokuba yiGhostRace (ezidweliswe phantsi kwe-CVE-2024-2193), le yindlela entsha ephuhliswe ngabaphandi baseVrije Universiteit Amsterdam kunye ne-IBM ukuze basebenzise indlela yokuqikelela ekhoyo kwiiprosesa zangoku ezivela kwi-Intel, AMD, ARM kunye ne-IBM.
Abaphandi bakhankanya ukuba, I-GhostRace igxile ekulawuleni iimeko zogqatso oluqikelelwayo ukufikelela kwiindawo zememori ezikhululwe ngaphambili, ezinokuthi khokelela ekutsalweni kwedatha ebuthathaka kwi Linux kernel, ngakumbi kwiimeko zokubona apho umhlaseli okwinkqubo yeendwendwe angabeka esichengeni ukhuseleko lwenkqubo yenginginya okanye ezinye iinkqubo zeendwendwe.
Uhlaselo lusebenza njani isekelwe kwintelekelelo yokuphunyezwa kwemiyalelo enemiqathango kunye primitives ungqamaniso ukuthunga, njenge-mutex kunye ne-spinlock.
Ukuba iprosesa iqikelela ngokungalunganga amasebe kwikhowudi ephatha le misebenzi, ufikelelo oluqikelelwayo lunokwenziwa kwinkumbulo esele ikhululiwe. Nangona iprosesa ilahla olu fikelelo emva kokubona ukucingelwa gwenxa, umkhondo wokwenziwa uhlala kwi-cache kwaye unokufunyanwa kwakhona kusetyenziswa iindlela zokuhlalutya itshaneli esecaleni.
I-GhostRace ifuna ubukho bolandelelwano lwemiyalelo ethile kwi-kernel, yaziwa njenge izixhobo, ezisetyenziselwa ukubulawa okuqikelelwayo ngokuxhomekeke kwiimeko zangaphandle ezilawulwa ngumhlaseli. Ezi zixhobo Zenziwe kumacandelo ekhowudi apho urhulumente ukhangelwa kwi-loop engapheliyo kwaye uphume kwilophu emva kokususa isitshixo sofikelelo kwisixhobo. Oku kukuvumela ukuba uqalise ngobuxoki kwaye wenze imiyalelo ekhuselweyo ngesitshixo, nangona isibonelelo sihlala sitshixiwe.
Ngexesha lokuhlalutya ubuthathaka, eyenziwe kwi-Linux kernel code 5.15.83, ubukho bezixhobo ezili-1283 zatyhilwa ezinokukhokelela kufikelelo oluqikelelwayo kwinkumbulo esele ikhutshiwe. Olu hlobo lohlaselo lubonisa umngcipheko onokubakho kwiinkqubo ze-virtualization, nayiphi na i-kernel yenkqubo yokusebenza, kunye neenkqubo ezisebenzisa i-thread synchronization primitives engqinisiswe ngeengxelo ezinemiqathango kwaye ziqhube kwiiplatifti ezivumela ukuphunyezwa okuqikelelwayo kwemisebenzi yesebe, njenge x86, ARM , RISC-V, phakathi kwabanye.
Ukuvavanya ukuba sesichengeni, abaphandi iphuhlise iprototype yokuxhaphaza ebonisa ukusebenza kakuhle del ukuhlaselwa ngokuvumela ukutsalwa yedatha evela kwimemori ye-Linux kernel ene-throughput ye-12 KB ngesekhondi kunye nenqanaba lokuthembeka elifana nokuhlaselwa kweklasi yeSpecter.
Los Abaphuhlisi be-Linux kernel kunye neenkampani zokuvelisa i-CPU zazisiwe ngale ngxaki ekupheleni kuka-2023. I-AMD sele ipapashe ingxelo malunga nokuba sesichengeni kwaye icebisa ukuba kusetyenziswe iindlela eziqhelekileyo zokukhusela kuhlaselo olufana neSpecter v1. Kwelinye icala, i-Intel kunye ne-ARM azikaphenduli kwesi saziso.
Nangona kunjalo Abaphuhlisi be-Linux kernel abanazo izicwangciso zangoku zokuphumeza uthotho lweeprimitives ungqamaniso Ngenxa yokulahleka kokusebenza, sele befake izithintelo ukukhusela kwi-IPI Storming exploit technique (CVE-2024-26602). Le ndlela yokuhlasela ibandakanya ukuphazamisa inkqubo ngexesha elifanelekileyo ukubonelela ngefestile yexesha lofikelelo oluqikelelwayo kwinkumbulo ekhululweyo.
Ukunciphisa olu hlobo lohlaselo, se iceba ukusebenzisa uthotho lwezinto zakudala ungqamaniso ngokubandakanya ingxelo ye-LFENCE emva kwenkcazo ye-cmpxchq ejonga isimo sokutshixa. Nangona kunjalo, Lo mlinganiselo wokhuseleko unesohlwayo sokusebenza esimalunga ne-5% kwibenchmark ye-LMBench, kuba ingxelo ye-LFENCE ivala umiliselo olulindelekileyo lweengxelo ezilandelayo phambi kokwenza yonke imisebenzi yangaphambili.
Kwimeko ye-hypervisor Xen, abaphuhlisi balungiselele utshintsho ukuphumeza i LOCK_HARDEN indlela yokutshixa ekhuselweyo, efana ne BRANCH_HARDEN indlela esetyenziswa ngasentla. Nangona kunjalo, ngenxa yeempembelelo zokusebenza ezimbi ezinokubakho kunye nokunqongophala kobungqina bohlaselo kwi-Xen, imo ye-LOCK_HARDEN ivaliwe ngokungagqibekanga.
ekugqibeleni ukuba ukhona unomdla wokwazi ngakumbi ngayo, ungajonga iinkcukacha kwi eli khonkco lilandelayo.