{"id":100574,"date":"2021-06-22T16:24:20","date_gmt":"2021-06-22T14:24:20","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimosti-v-podsisteme-ebpf-pozvolyayushhie-obojti-zashhitu-ot-atak-klassa-spectre"},"modified":"2021-06-22T16:24:20","modified_gmt":"2021-06-22T14:24:20","slug":"uyazvimosti-v-podsisteme-ebpf-pozvolyayushhie-obojti-zashhitu-ot-atak-klassa-spectre","status":"publish","type":"post","link":"https:\/\/prohoster.info\/ro\/blog\/news\/uyazvimosti-v-podsisteme-ebpf-pozvolyayushhie-obojti-zashhitu-ot-atak-klassa-spectre","title":{"rendered":"Vulnerabilit\u0103\u021bi \u00een subsistemul eBPF, care permit ocolirea protec\u021biei \u00eempotriva atacurilor de tip Spectre","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

O vulnerabilitate a fost identificat\u0103 \u00een nucleul Linux (CVE-2021-33624), care permite utilizarea subsistemului eBPF pentru ocolirea protec\u021biei \u00eempotriva vulnerabilit\u0103\u021bilor de tip Spectre, oferind posibilitatea de a determina con\u021binutul memoriei \u00een urma cre\u0103rii de condi\u021bii pentru executarea speculativ\u0103 a anumitor opera\u021biuni. Atacul Spectre necesit\u0103 existen\u021ba \u00eentr-un cod privilegiat a unei secven\u021be specifice de comenzi care conduc la executarea speculativ\u0103 a instruc\u021biunilor. Prin manipularea programelor BPF transmise pentru executare, se poate genera astfel de instruc\u021biuni \u00een eBPF, ceea ce poate duce la scurgeri de con\u021binut al memoriei nucleului \u0219i al unor zone arbitrare ale memoriei fizice prin canale externe. <\/p>\n

Vulnerabilitatea este cauzat\u0103 de lipsurile din verificator, care este utilizat pentru a identifica erorile \u0219i activit\u0103\u021bile necorespunz\u0103toare \u00een programele BPF. Verificatorul analizeaz\u0103 posibilele c\u0103i de execu\u021bie a codului, dar trece cu vederea variantele de ramificare care sunt invalide din punct de vedere semantic conform arhitecturii setului de comenzi. Atunci c\u00e2nd se execut\u0103 un program BPF, variantele de ramificare care nu sunt luate \u00een considerare de verificator pot fi prezise gre\u0219it de procesor \u0219i executate \u00een mod speculativ. De exemplu, \u00een analiza opera\u021biei \u201eload\u201d, verificatorul presupune c\u0103 registrul utilizat \u00een instruc\u021biune con\u021bine o adres\u0103 al c\u0103rei valoare se afl\u0103 \u00eentotdeauna \u00een limitele specificate, dar un atacator ar putea crea condi\u021bii \u00een care procesorul va \u00eencerca s\u0103 execute speculativ o opera\u021biune cu o adres\u0103 care nu respect\u0103 condi\u021biile de verificare. <\/p>\n

Problema se manifest\u0103 \u00eencep\u00e2nd cu lansarea nucleului 4.15 \u0219i a fost remediat\u0103 sub form\u0103 de patch-uri (1, 2, 3, 4). \u00cen distribu\u021biile de sistem, vulnerabilitatea r\u0103m\u00e2ne nerezolvat\u0103 (Debian, RHEL, Ubuntu, Fedora, SUSE, Arch). <\/p>\n

De asemenea, merit\u0103 s\u0103 men\u021bion\u0103m un comentariu despre impactul asupra performan\u021bei m\u0103surilor de protec\u021bie \u00eempotriva vulnerabilit\u0103\u021bilor de tip Spectre. \u00cen comentariu sunt sintetizate rezultatele optimiz\u0103rii debugger-ului rr (Record and Replay), creat c\u00e2ndva \u00een Mozilla pentru a depana erorile greu de replicat \u00een Firefox. Cache-ul apelurilor sistemului utilizate pentru a verifica existen\u021ba directorilor a permis reducerea timpului de execu\u021bie al op\u021biunii \u201err sources\u201d pentru un proiect de testare de la 3 minute \u0219i 19 secunde la 36 de secunde. <\/p>\n

Autorul optimiz\u0103rii a decis s\u0103 verifice cum se va schimba performan\u021ba dup\u0103 dezactivarea protec\u021biei \u00eempotriva Spectre. Dup\u0103 \u00eenc\u0103rcarea sistemului cu parametrul \u201emitigations=off\u201d, timpul de execu\u021bie pentru \u201err sources\u201d f\u0103r\u0103 optimizare a fost de 2 minute \u0219i 5 secunde (de 1,6 ori mai rapid), iar cu optimizarea - 33 de secunde (cu 9% mai rapid). Este interesant c\u0103 dezactivarea protec\u021biei \u00eempotriva Spectre nu doar c\u0103 a redus timpul de execu\u021bie a codului la nivel de nucleu (de la 2m9s la 1m32s), dar a \u0219i dublat timpul de execu\u021bie \u00een spa\u021biul utilizatorului (de la 1m9s la 0m33s), probabil din cauza sc\u0103derii eficien\u021bei func\u021bion\u0103rii cache-ului CPU \u0219i a reset\u0103rilor TLB atunci c\u00e2nd protec\u021bia \u00eempotriva Spectre este activat\u0103.
\n
Sursa: opennet.ro<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u044f\u0434\u0440\u0435 Linux \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c (CVE-2021-33624), \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u044c \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0443 \u0435BPF \u0434\u043b\u044f \u043e\u0431\u0445\u043e\u0434\u0430 \u0437\u0430\u0449\u0438\u0442\u044b \u043e\u0442 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u043a\u043b\u0430\u0441\u0441\u0430 Spectre, \u0434\u0430\u044e\u0449\u0438\u0445 \u0432\u043e\u0437\u043c\u043e\u0436\u043d\u043e\u0441\u0442\u044c \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0438\u0442\u044c \u0441\u043e\u0434\u0435\u0440\u0436\u0438\u043c\u043e\u0435 \u043f\u0430\u043c\u044f\u0442\u0438 \u0432 \u0440\u0435\u0437\u0443\u043b\u044c\u0442\u0430\u0442\u0435 \u0441\u043e\u0437\u0434\u0430\u043d\u0438\u044f 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\u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044e \u0438\u043d\u0441\u0442\u0440\u0443\u043a\u0446\u0438\u0439. \u0427\u0435\u0440\u0435\u0437 \u043c\u0430\u043d\u0438\u043f\u0443\u043b\u044f\u0446\u0438\u044e \u0441 \u043f\u0435\u0440\u0435\u0434\u0430\u0432\u0430\u0435\u043c\u044b\u043c\u0438 \u0434\u043b\u044f \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f BPF-\u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u0430\u043c\u0438 \u043c\u043e\u0436\u043d\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-100574","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\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\udd47Vulnerabilit\u0103\u021bi \u00een subsistemul eBPF care permit ocolirea protec\u021biei \u00eempotriva atacurilor de tip Spectre | ProHoster","description":"O vulnerabilitate a fost descoperit\u0103 \u00een nucleul Linux (CVE-2021-33624), care permite utilizarea subsistemului eBPF pentru a ocoli protec\u021bia \u00eempotriva vulnerabilit\u0103\u021bilor de tip Spectre, permi\u021b\u00e2nd astfel determinarea con\u021binutului 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