{"id":100636,"date":"2021-06-30T22:23:10","date_gmt":"2021-06-30T20:23:10","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-speczifichnom-dlya-cpu-amd-kode-kvm-pozvolyayushhaya-vypolnit-kod-vne-gostevoj-sistemy"},"modified":"2021-06-30T22:23:10","modified_gmt":"2021-06-30T20:23:10","slug":"uyazvimost-v-speczifichnom-dlya-cpu-amd-kode-kvm-pozvolyayushhaya-vypolnit-kod-vne-gostevoj-sistemy","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sv\/blog\/news\/uyazvimost-v-speczifichnom-dlya-cpu-amd-kode-kvm-pozvolyayushhaya-vypolnit-kod-vne-gostevoj-sistemy","title":{"rendered":"S\u00e5rbarhet i AMD-specifik CPU-kod i KVM som till\u00e5ter att k\u00f6ra kod utanf\u00f6r g\u00e4stsystmet","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Forskare fr\u00e5n Google Project Zero har uppt\u00e4ckt en s\u00e5rbarhet (CVE-2021-29657) i KVM-hypervisorn som levereras med Linux-k\u00e4rnan, vilket g\u00f6r det m\u00f6jligt att kringg\u00e5 isoleringen av g\u00e4stsystemet och k\u00f6ra egen kod i v\u00e4rdmilj\u00f6n. Problemet finns i koden som anv\u00e4nds p\u00e5 system med AMD-processorer (modulen kvm-amd.ko) och visar sig inte f\u00f6r Intel-processorer. <\/p>\n

Forskarna har tagit fram en fungerande prototyp av en exploit som m\u00f6jligg\u00f6r att k\u00f6ra en root shell i v\u00e4rdmilj\u00f6n fr\u00e5n en g\u00e4stmilj\u00f6 p\u00e5 ett system med AMD Epyc 7351P-processor och Linux 5.10-k\u00e4rna. Det noteras att detta \u00e4r den f\u00f6rsta s\u00e5rbarheten av typen 'guest-to-host' i sj\u00e4lva hypervisorn. KVM<\/a>, inte relaterad till fel i komponenter som k\u00f6rs i anv\u00e4ndarutrymmet, s\u00e5som QEMU. En l\u00f6sning har godk\u00e4nts f\u00f6r k\u00e4rnan i slutet av mars. Problemet uppst\u00e5r med Linux-k\u00e4rna 5.10-rc1 och str\u00e4cker sig fram till v5.12-rc6, dvs. det omfattar endast k\u00e4rnorna 5.10 och 5.11 (de flesta stabila distributioner p\u00e5verkas inte av problemet). <\/p>\n

Problemet finns i mekanismen nested_svm_vmrun, implementerad med AMD SVM (Secure Virtual Machine)-till\u00e4gget, som m\u00f6jligg\u00f6r att k\u00f6ra inb\u00e4ddade g\u00e4stsystem. F\u00f6r att korrekt implementera denna funktionalitet m\u00e5ste hypervisorn f\u00e5nga alla SVM-instruktioner som k\u00f6rs i g\u00e4stsystemen, emulera deras beteende och synkronisera tillst\u00e5ndet med h\u00e5rdvaran, vilket \u00e4r en ganska komplex uppgift. Efter att ha analyserat den f\u00f6reslagna implementationen i KVM fann forskarna en logisk felaktighet, vilket g\u00f6r det m\u00f6jligt att p\u00e5verka inneh\u00e5llet i MSR-register (Model-Specific Register) i v\u00e4rden fr\u00e5n g\u00e4stsystemet, vilket kan utnyttjas f\u00f6r att k\u00f6ra kod p\u00e5 v\u00e4rdniv\u00e5. <\/p>\n

Mer specifikt leder k\u00f6rningen av operationen VMRUN fr\u00e5n det andra niv\u00e5g\u00e4stsystemet (L2, som k\u00f6rs fr\u00e5n ett annat g\u00e4sts system) till det andra anropet av nested_svm_vmrun och skador p\u00e5 strukturen svm->nested.hsave, som \u00e5samkas data fr\u00e5n L2-g\u00e4stsystemets vmcb. Som ett resultat uppst\u00e5r en situation d\u00e4r man p\u00e5 niv\u00e5n f\u00f6r g\u00e4stsystemet L2 kan frig\u00f6ra minne i strukturen svm->nested.msrpm, d\u00e4r MSR-biten lagras, trots att den fortfarande anv\u00e4nds, och f\u00e5 \u00e5tkomst till v\u00e4rdsystemets MSR.
\n
K\u00e4lla: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0418\u0441\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u0438 \u0438\u0437 \u043a\u043e\u043c\u0430\u043d\u0434\u044b Google Project Zero \u0432\u044b\u044f\u0432\u0438\u043b\u0438 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-29657) \u0432 \u043f\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u043c\u043e\u043c \u0432 \u0441\u043e\u0441\u0442\u0430\u0432\u0435 \u044f\u0434\u0440\u0430 Linux \u0433\u0438\u043f\u0435\u0440\u0432\u0438\u0437\u043e\u0440\u0435 KVM, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0443\u044e \u043e\u0431\u043e\u0439\u0442\u0438 \u0438\u0437\u043e\u043b\u044f\u0446\u0438\u044e \u0433\u043e\u0441\u0442\u0435\u0432\u043e\u0439 \u0441\u0438\u0441\u0442\u0435\u043c\u044b \u0438 \u0432\u044b\u043f\u043e\u043b\u043d\u0438\u0442\u044c \u0441\u0432\u043e\u0439 \u043a\u043e\u0434 \u043d\u0430 \u0441\u0442\u043e\u0440\u043e\u043d\u0435 \u0445\u043e\u0441\u0442-\u043e\u043a\u0440\u0443\u0436\u0435\u043d\u0438\u044f. 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\u0433\u043e\u0441\u0442\u0435\u0432\u043e\u0433\u043e […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-100636","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47S\u00e5rbarhet i KVM:s CPU-specifika kod f\u00f6r AMD, som m\u00f6jligg\u00f6r att k\u00f6ra kod utanf\u00f6r g\u00e4stsystemet | ProHoster","description":"Forskare fr\u00e5n Google Project Zero har identifierat en s\u00e5rbarhet (CVE-2021-29657) i KVM-hypervisorn som levereras med Linux-k\u00e4rnan, vilket m\u00f6jligg\u00f6r att kringg\u00e5 isoleringen av 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