A Linux kernel vulnerability (CVE-2021-33624) has been identified, allowing the use of the eBPF subsystem to bypass protections against Spectre-class vulnerabilities, which can determine the contents of memory by creating conditions for speculative execution of certain operations. An attack leveraging Spectre requires a specific sequence of commands in privileged code that leads to the speculative execution of instructions. By manipulating the BPF programs passed for execution, it is possible to generate similar instructions in eBPF, leading to kernel memory content leakage and arbitrary physical memory areas through side channels. <\/p>\n
A sebezhet\u0151s\u00e9get a BPF programokban fell\u00e9p\u0151 hib\u00e1k \u00e9s helytelen tev\u00e9kenys\u00e9gek \u00e9szlel\u00e9se c\u00e9lj\u00e1b\u00f3l alkalmazott ellen\u0151rz\u0151 eszk\u00f6z hi\u00e1nyoss\u00e1gai okozz\u00e1k. Az ellen\u0151r a k\u00f3d v\u00e9grehajt\u00e1s\u00e1nak lehets\u00e9ges \u00fatvonalait vizsg\u00e1lja, de figyelmen k\u00edv\u00fcl hagyja azokat az el\u00e1gaz\u00e1si lehet\u0151s\u00e9geket, amelyek a parancsok architekt\u00far\u00e1j\u00e1nak szemantikai szempontj\u00e1b\u00f3l \u00e9rv\u00e9nytelenek. A BPF programok v\u00e9grehajt\u00e1sa sor\u00e1n a folyamatort olyan el\u00e1gaz\u00e1sok is megt\u00e9veszthetnek, amelyeket az ellen\u0151r nem vett figyelembe, ami spekulat\u00edv m\u00f3don v\u00e9grehajt\u00e1sra ker\u00fclhet. P\u00e9ld\u00e1ul a «load» m\u0171velet elemz\u00e9se sor\u00e1n az ellen\u0151r azt felt\u00e9telezi, hogy a parancs egy olyan regisztert haszn\u00e1l, amelynek c\u00edme mindig megadott hat\u00e1rok k\u00f6z\u00f6tt van, de a t\u00e1mad\u00f3 olyan k\u00f6r\u00fclm\u00e9nyeket teremthet, amelyek mellett a processzor spekulat\u00edvan megpr\u00f3b\u00e1lja v\u00e9grehajtani a m\u0171veletet egy olyan c\u00edmmel, amely nem felel meg az ellen\u0151rz\u00e9s felt\u00e9teleinek. <\/p>\n
The problem manifests starting from kernel release 4.15 and has been addressed in the form of patches (1, 2, 3, 4). In the distributions, the vulnerability remains unaddressed (Debian, RHEL, Ubuntu, Fedora, SUSE, Arch). <\/p>\n
Tov\u00e1bbi megjegyz\u00e9sk\u00e9nt eml\u00edthetj\u00fck a Spectre sebezhet\u0151s\u00e9gek elleni v\u00e9delmi eszk\u00f6z\u00f6k teljes\u00edtm\u00e9ny\u00e9re gyakorolt hat\u00e1s\u00e1t. A megjegyz\u00e9s \u00f6sszegzi a Mozilla \u00e1ltal a Firefoxban el\u0151fordul\u00f3 nehezen reproduk\u00e1lhat\u00f3 hib\u00e1k hibakeres\u00e9s\u00e9re kifejlesztett rr (Record and Replay) debuggere optimaliz\u00e1l\u00e1si eredm\u00e9nyeit. A k\u00f6nyvt\u00e1rak l\u00e9tez\u00e9s\u00e9nek ellen\u0151rz\u00e9s\u00e9re haszn\u00e1lt rendszerh\u00edv\u00e1sok gyors\u00edt\u00f3t\u00e1raz\u00e1sa lehet\u0151v\u00e9 tette, hogy az «rr sources» m\u0171velet a tesztprojektn\u00e9l 3 perc 19 m\u00e1sodpercr\u0151l 36 m\u00e1sodpercre cs\u00f6kkenjen. <\/p>\n
Az optimaliz\u00e1l\u00e1s szerz\u0151je meg akarta vizsg\u00e1lni, mennyire v\u00e1ltozik a teljes\u00edtm\u00e9ny a Spectre elleni v\u00e9delem letilt\u00e1sa ut\u00e1n. A rendszer «mitigations=off» param\u00e9terrel t\u00f6rt\u00e9n\u0151 ind\u00edt\u00e1sa ut\u00e1n az «rr sources» v\u00e9grehajt\u00e1si ideje optimaliz\u00e1l\u00e1s n\u00e9lk\u00fcl 2 perc 5 m\u00e1sodperc (1,6-szor gyorsabb) lett, m\u00edg optimaliz\u00e1l\u00e1ssal 33 m\u00e1sodperc (9%-kal gyorsabb). \u00c9rdekes, hogy a Spectre elleni v\u00e9delem letilt\u00e1sa nemcsak 1,4-szer cs\u00f6kkentette a k\u00f3d v\u00e9grehajt\u00e1si idej\u00e9t a kernel szintj\u00e9n (2m9s-r\u00f3l 1m32s-ra), hanem k\u00e9tszer cs\u00f6kkentette a felhaszn\u00e1l\u00f3i t\u00e9r v\u00e9grehajt\u00e1si idej\u00e9t is (1m9s-r\u0151l 0m33s-ra), val\u00f3sz\u00edn\u0171leg a processzor gyors\u00edt\u00f3t\u00e1r\u00e1nak \u00e9s a TLB vissza\u00e1ll\u00edt\u00e1sainak cs\u00f6kkent hat\u00e9konys\u00e1ga miatt a Spectre elleni v\u00e9delem bekapcsolt \u00e1llapot\u00e1ban. \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 \u0443\u0441\u043b\u043e\u0432\u0438\u0439 \u0434\u043b\u044f \u0441\u043f\u0435\u043a\u0443\u043b\u044f\u0442\u0438\u0432\u043d\u043e\u0433\u043e \u0432\u044b\u043f\u043e\u043b\u043d\u0435\u043d\u0438\u044f \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0451\u043d\u043d\u044b\u0445 \u043e\u043f\u0435\u0440\u0430\u0446\u0438\u0439. \u0414\u043b\u044f \u0430\u0442\u0430\u043a\u0438 Spectre \u0442\u0440\u0435\u0431\u0443\u0435\u0442\u0441\u044f \u043d\u0430\u043b\u0438\u0447\u0438\u0435 \u0432 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u043e\u043c \u043a\u043e\u0434\u0435 \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0451\u043d\u043d\u043e\u0439 \u043f\u043e\u0441\u043b\u0435\u0434\u043e\u0432\u0430\u0442\u0435\u043b\u044c\u043d\u043e\u0441\u0442\u0438 \u043a\u043e\u043c\u0430\u043d\u0434, \u043f\u0440\u0438\u0432\u043e\u0434\u044f\u0449\u0438\u0445 \u043a \u0441\u043f\u0435\u043a\u0443\u043b\u044f\u0442\u0438\u0432\u043d\u043e\u043c\u0443 \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 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Forr\u00e1s: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"