{"id":99293,"date":"2021-02-28T10:22:45","date_gmt":"2021-02-28T08:22:45","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu"},"modified":"2021-02-28T10:22:45","modified_gmt":"2021-02-28T08:22:45","slug":"v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu","status":"publish","type":"post","link":"https:\/\/prohoster.info\/cs\/blog\/news\/v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu","title":{"rendered":"Do j\u00e1dra Linuxu 5.12 byla p\u0159ijata podsyst\u00e9m KFence pro odhalov\u00e1n\u00ed chyb p\u0159i pr\u00e1ci s pam\u011bt\u00ed.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Sou\u010d\u00e1st\u00ed vyv\u00edjen\u00e9ho j\u00e1dra Linux 5.12 je implementace mechanismu KFence (Kernel Electric Fence), kter\u00fd kontroluje pr\u00e1ci s pam\u011bt\u00ed, odhaluje p\u0159ete\u010den\u00ed buffer\u016f, p\u0159\u00edstupy k pam\u011bti po uvoln\u011bn\u00ed a dal\u0161\u00ed podobn\u00e9 chyby. <\/p>\n

Podobn\u00e1 funk\u010dnost ji\u017e byla p\u0159\u00edtomna v j\u00e1dru jako mo\u017enost sestaven\u00ed KASAN (kernel address sanitizer, vyu\u017e\u00edv\u00e1 Address Sanitizer v modern\u00edch gcc a clang) \u2014 av\u0161ak byla prim\u00e1rn\u011b ur\u010dena pro ladic\u00ed pou\u017eit\u00ed. Podsystem KFence se od KASAN li\u0161\u00ed vysokou rychlost\u00ed, co\u017e umo\u017e\u0148uje tuto funk\u010dnost vyu\u017e\u00edvat i na j\u00e1drech ve v\u00fdrobn\u00edch syst\u00e9mech. <\/p>\n

Pou\u017eit\u00ed v produk\u010dn\u00edch syst\u00e9mech umo\u017en\u00ed odhalov\u00e1n\u00ed chyb v pam\u011bti, kter\u00e9 se neprojevuj\u00ed v testovac\u00edch b\u011bz\u00edch a objevuj\u00ed se pouze p\u0159i pracovn\u00edch z\u00e1t\u011b\u017e\u00edch nebo po del\u0161\u00ed dob\u011b provozu (p\u0159i velk\u00e9m uptime). Nav\u00edc pou\u017eit\u00ed KFence v produk\u010dn\u00edch syst\u00e9mech v\u00fdrazn\u011b zv\u00fd\u0161\u00ed po\u010det stroj\u016f zapojen\u00fdch do kontroly pr\u00e1ce j\u00e1dra s pam\u011bt\u00ed. <\/p>\n

Minim\u00e1ln\u00ed re\u017eijn\u00ed n\u00e1klady, kter\u00e9 nez\u00e1vis\u00ed na z\u00e1t\u011b\u017ei, jsou v KFence dosa\u017eeny d\u00edky zaveden\u00ed str\u00e1nek ochrany (guard pages) do haldy v pevn\u00fdch intervalech. Po uplynut\u00ed doby chr\u00e1n\u00edc\u00edho intervalu KFence p\u0159es standardn\u00ed syst\u00e9m p\u0159id\u011blov\u00e1n\u00ed pam\u011bti (SLAB nebo SLUB allocator) p\u0159id\u00e1v\u00e1 dal\u0161\u00ed str\u00e1nku ochrany z objektov\u00e9ho fondu KFence a za\u010d\u00edn\u00e1 nov\u00fd odpo\u010det \u010dasova\u010de. Ka\u017ed\u00fd objekt KFence je um\u00edst\u011bn na samostatn\u00e9 str\u00e1nce pam\u011bti a str\u00e1nky pam\u011bti na lev\u00e9 a prav\u00e9 hranici tvo\u0159\u00ed str\u00e1nky ochrany (guard pages), jejich\u017e velikost se vyb\u00edr\u00e1 n\u00e1hodn\u011b. <\/p>\n

T\u00edmto zp\u016fsobem jsou str\u00e1nky s objekty odd\u011bleny str\u00e1nkami ochrany, kter\u00e9 jsou nastaveny tak, aby generovaly \u201epage fault\u201c p\u0159i jak\u00e9mkoli p\u0159\u00edstupu. Pro odhalen\u00ed z\u00e1pisov\u00fdch operac\u00ed p\u0159es hranici bufferu uvnit\u0159 str\u00e1nek s objekty se nav\u00edc vyu\u017e\u00edvaj\u00ed \u201e\u010derven\u00e9 z\u00f3ny\u201c na z\u00e1klad\u011b \u0161ablon, kter\u00e9 zab\u00edraj\u00ed pam\u011b\u0165, je\u017e nen\u00ed pou\u017e\u00edv\u00e1na objekty a z\u016fst\u00e1v\u00e1 p\u0159i zarovn\u00e1n\u00ed velikosti str\u00e1nek pam\u011bti. \u2014+------+-------+------+ : O | xxxxxxxxx | | xxxxxxxxx | B : | xxxxxxxxx | : B | xxxxxxxxx | | x GUARD x | J : RED- | x GUARD x | RED- : J | x GUARD x | | xxxxxxxxx | E : ZONE | xxxxxxxxx | ZONE : E | xxxxxxxxx | | xxxxxxxxx | C : | xxxxxxxxx | : C | xxxxxxxxx | | xxxxxxxxx | T : | xxxxxxxxx | : T | xxxxxxxxx | \u2014+------+-------+------+\u2014+------+-------+------+\u2014+------+-------+------+\u2014+------+-------+------+\u2014+------+-------+------+ <\/p>\n

V p\u0159\u00edpad\u011b pokusu o p\u0159\u00edstup do oblasti mimo hranice bufferu operace zas\u00e1hne str\u00e1nku ochrany, co\u017e vede k vygenerov\u00e1n\u00ed \u201epage fault\u201c, kterou zachyt\u00ed KFence a zap\u00ed\u0161e do logu \u00fadaje o zji\u0161t\u011bn\u00e9m probl\u00e9mu. Ve v\u00fdchoz\u00edm nastaven\u00ed KFence nezablokov\u00e1v\u00e1 chybu a pouze vyd\u00e1v\u00e1 varov\u00e1n\u00ed do logu, ale je k dispozici nastaven\u00ed \u201epanic_on_warn\u201c, kter\u00e9 umo\u017e\u0148uje v p\u0159\u00edpad\u011b zji\u0161t\u011bn\u00ed chyby p\u0159ev\u00e9st j\u00e1dro do stavu p\u00e1du (panic).
\n
Zdroj: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u0441\u043e\u0441\u0442\u0430\u0432 \u043d\u0430\u0445\u043e\u0434\u044f\u0449\u0435\u0433\u043e\u0441\u044f \u0432 \u0440\u0430\u0437\u0440\u0430\u0431\u043e\u0442\u043a\u0435 \u044f\u0434\u0440\u0430 Linux 5.12 \u0432\u043a\u043b\u044e\u0447\u0435\u043d\u0430 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u044f \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 KFence (Kernel Electric Fence), \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u043f\u0440\u043e\u0432\u0435\u0440\u044f\u0435\u0442 \u0440\u0430\u0431\u043e\u0442\u0443 \u0441 \u043f\u0430\u043c\u044f\u0442\u044c\u044e, \u043e\u0442\u043b\u0430\u0432\u043b\u0438\u0432\u0430\u044f \u0432\u044b\u0445\u043e\u0434 \u0437\u0430 \u0433\u0440\u0430\u043d\u0438\u0446\u044b \u0431\u0443\u0444\u0435\u0440\u043e\u0432, \u043e\u0431\u0440\u0430\u0449\u0435\u043d\u0438\u044f \u043a \u043f\u0430\u043c\u044f\u0442\u0438 \u043f\u043e\u0441\u043b\u0435 \u043e\u0441\u0432\u043e\u0431\u043e\u0436\u0434\u0435\u043d\u0438\u044f \u0438 \u0434\u0440\u0443\u0433\u0438\u0435 \u043e\u0448\u0438\u0431\u043a\u0438 \u043f\u043e\u0434\u043e\u0431\u043d\u043e\u0433\u043e \u043a\u043b\u0430\u0441\u0441\u0430. \u041f\u043e\u0434\u043e\u0431\u043d\u0430\u044f \u0444\u0443\u043d\u043a\u0446\u0438\u043e\u043d\u0430\u043b\u044c\u043d\u043e\u0441\u0442\u044c \u0443\u0436\u0435 \u043f\u0440\u0438\u0441\u0443\u0442\u0441\u0442\u0432\u043e\u0432\u0430\u043b\u0430 \u0432 \u044f\u0434\u0440\u0435 \u0432 \u0432\u0438\u0434\u0435 \u043e\u043f\u0446\u0438\u0438 \u0441\u0431\u043e\u0440\u043a\u0438 KASAN (kernel address sanitizer, \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u0435\u0442 Address Sanitizer \u0432 \u0441\u043e\u0432\u0440\u0435\u043c\u0435\u043d\u043d\u044b\u0445 gcc […]<\/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-99293","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\udd47Do j\u00e1dra Linux 5.12 byla p\u0159ijata podsystem KFence pro detekci chyb p\u0159i pr\u00e1ci s pam\u011bt\u00ed | ProHoster","description":"Implementace mechanismu KFence (Kernel Electric Fence), kter\u00fd kontroluje pr\u00e1ci s pam\u011bt\u00ed a zachycuje v\u00fdstupy za hranice vyrovn\u00e1vac\u00edch pam\u011bt\u00ed, je sou\u010d\u00e1st\u00ed vyv\u00edjen\u00e9ho j\u00e1dra Linux 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\u043f\u0430\u043c\u044f\u0442\u044c\u044e | ProHoster","og:description":"\u0412 \u0441\u043e\u0441\u0442\u0430\u0432 \u043d\u0430\u0445\u043e\u0434\u044f\u0449\u0435\u0433\u043e\u0441\u044f \u0432 \u0440\u0430\u0437\u0440\u0430\u0431\u043e\u0442\u043a\u0435 \u044f\u0434\u0440\u0430 Linux 5.12 \u0432\u043a\u043b\u044e\u0447\u0435\u043d\u0430 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u044f \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 KFence (Kernel Electric Fence), \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u043f\u0440\u043e\u0432\u0435\u0440\u044f\u0435\u0442 \u0440\u0430\u0431\u043e\u0442\u0443 \u0441 \u043f\u0430\u043c\u044f\u0442\u044c\u044e, \u043e\u0442\u043b\u0430\u0432\u043b\u0438\u0432\u0430\u044f \u0432\u044b\u0445\u043e\u0434 \u0437\u0430 \u0433\u0440\u0430\u043d\u0438\u0446\u044b \u0431\u0443\u0444\u0435\u0440\u043e\u0432, \u043e\u0431\u0440\u0430\u0449\u0435\u043d\u0438\u044f \u043a \u043f\u0430\u043c\u044f\u0442\u0438 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