{"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\/hu\/blog\/news\/v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu","title":{"rendered":"A Linux 5.12 kernelbe beker\u00fclt a KFence alrendszer a mem\u00f3riahaszn\u00e1lati hib\u00e1k felder\u00edt\u00e9s\u00e9re.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

A Linux 5.12 verzi\u00f3j\u00e1ba be\u00e9p\u00edtett\u00e9k a KFence (Kernel Electric Fence) mechanizmus megval\u00f3s\u00edt\u00e1s\u00e1t, amely a mem\u00f3ria kezel\u00e9s\u00e9t ellen\u0151rzi, \u00e9s kifog\u00e1solja a buffersz\u00e9li t\u00fall\u00e9p\u00e9seket, a mem\u00f3riacs\u00f6kkent\u00e9seket k\u00f6vet\u0151 hozz\u00e1f\u00e9r\u00e9seket \u00e9s m\u00e1s hasonl\u00f3 hib\u00e1kat. <\/p>\n

Ez a funkci\u00f3 m\u00e1r l\u00e9tezett a kernel alapj\u00e1ban a KASAN (kernel address sanitizer) \u00f6sszeszerel\u00e9si opci\u00f3k\u00e9nt, amely a modern gcc \u00e9s clang Address Sanitizer-t haszn\u00e1lja - de f\u0151k\u00e9nt hibakeres\u00e9si c\u00e9lokra pozicion\u00e1lt\u00e1k. A KFence alrendszer a KASAN-nal szemben nagy sebess\u00e9ggel m\u0171k\u00f6dik, lehet\u0151v\u00e9 t\u00e9ve e funkci\u00f3 haszn\u00e1lat\u00e1t ak\u00e1r m\u0171k\u00f6d\u0151 rendszerek kerneljeiben is. <\/p>\n

Az \u00e9les rendszereken t\u00f6rt\u00e9n\u0151 alkalmaz\u00e1s lehet\u0151v\u00e9 teszi a mem\u00f3riakezel\u00e9si hib\u00e1k \u00e9szlel\u00e9s\u00e9t, amelyek nem jelentkeznek tesztel\u00e9s sor\u00e1n, hanem csak a munkaterhel\u00e9sek vagy hosszabb m\u0171k\u00f6d\u00e9s (nagy uptime) alatt. Ezen k\u00edv\u00fcl a KFence alkalmaz\u00e1sa \u00e9les rendszereken jelent\u0151sen n\u00f6velheti azoknak a g\u00e9peknek a sz\u00e1m\u00e1t, amelyek r\u00e9szt vesznek a kernel mem\u00f3riakezel\u00e9s\u00e9nek ellen\u0151rz\u00e9s\u00e9ben. <\/p>\n

A minim\u00e1lis, terhel\u00e9st\u0151l f\u00fcggetlen k\u00f6lts\u00e9geket a KFence a v\u00e9delmi oldalak (guard pages) beilleszt\u00e9s\u00e9vel \u00e9ri el a halomba, r\u00f6gz\u00edtett id\u0151k\u00f6z\u00f6kben. A k\u00f6vetkez\u0151 v\u00e9delmi id\u0151szak letelt\u00e9vel a KFence a szok\u00e1sos mem\u00f3riakezel\u0151 rendszeren (SLAB vagy SLUB allocator) kereszt\u00fcl hozz\u00e1ad egy \u00faj v\u00e9d\u0151oldalt a KFence objektumok medenc\u00e9j\u00e9b\u0151l, \u00e9s \u00faj id\u0151sz\u00e1ml\u00e1l\u00f3t ind\u00edt. Minden KFence objektumot egy k\u00fcl\u00f6n mem\u00f3riaoldalon helyeznek el, \u00e9s az oldalak bal \u00e9s jobb sz\u00e9lei v\u00e9d\u0151oldalakat (guard pages) alkotnak, amelyek m\u00e9rete v\u00e9letlenszer\u0171en ker\u00fcl meghat\u00e1roz\u00e1sra. <\/p>\n

\u00cdgy az objektumokat tartalmaz\u00f3 oldalak elv\u00e1laszt\u00f3dnak egym\u00e1st\u00f3l a v\u00e9delmi oldalakt\u00f3l, amelyek a b\u00e1rmilyen hivatkoz\u00e1s eset\u00e9n a 'page fault' gener\u00e1l\u00e1s\u00e1ra vannak be\u00e1ll\u00edtva. A buferr\u00f3l val\u00f3 \u00edr\u00e1si m\u0171veletek az objektumok k\u00f6z\u00f6tti oldalon t\u00f6rt\u00e9n\u0151 azonos\u00edt\u00e1sa \u00e9rdek\u00e9ben tov\u00e1bbi 'piros z\u00f3n\u00e1kat' haszn\u00e1lnak, amelyek mint\u00e1k alapj\u00e1n foglalj\u00e1k el az objektumok \u00e1ltal nem haszn\u00e1lt mem\u00f3ri\u00e1t, amely a mem\u00f3riaoldalak m\u00e9ret\u00e9nek igaz\u00edt\u00e1sakor marad. —+————+————+————+————+————+— | xxxxxxxxx | O : | xxxxxxxxx | : 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 | —+————+————+————+————+————+— <\/p>\n

Amikor megpr\u00f3b\u00e1lnak hozz\u00e1f\u00e9rni a buffer hat\u00e1rain k\u00edv\u00fcli ter\u00fclethez, a m\u0171velet beleker\u00fcl a v\u00e9delmi oldalba, ami 'page fault' gener\u00e1l\u00e1s\u00e1hoz vezet, melyet a KFence elfog, \u00e9s a logba \u00edrja a felismert probl\u00e9m\u00e1r\u00f3l sz\u00f3l\u00f3 adatokat. Alap\u00e9rtelmez\u00e9s szerint a KFence nem blokkolja a hib\u00e1t, csak figyelmeztet\u00e9st \u00edr ki a logba, de van lehet\u0151s\u00e9g a 'panic_on_warn' be\u00e1ll\u00edt\u00e1s\u00e1ra, amely lehet\u0151v\u00e9 teszi, hogy hiba eset\u00e9n a kernelt \u00f6sszeoml\u00e1si \u00e1llapotba \u00e1ll\u00edtsa (panic).
\n
Forr\u00e1s: 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\udd47A Linux 5.12 kernelbe integr\u00e1lt\u00e1k a KFence alrendszert a mem\u00f3riahaszn\u00e1lati hib\u00e1k azonos\u00edt\u00e1s\u00e1ra | ProHoster","description":"A fejleszt\u00e9s alatt \u00e1ll\u00f3 Linux 5.12 kernelbe beletartozik a KFence (Kernel Electric Fence) mechanizmus megval\u00f3s\u00edt\u00e1sa, amely ellen\u0151rzi a mem\u00f3riahaszn\u00e1latot, \u00e9s \u00e9szleli a buffer hat\u00e1rain t\u00fali hozz\u00e1f\u00e9r\u00e9seket \u00e9s a mem\u00f3ria ut\u00e1ni hivatkoz\u00e1sokat.","canonical_url":"https:\/\/prohoster.info\/hu\/blog\/news\/v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"hu_HU","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47\u0412 \u044f\u0434\u0440\u043e Linux 5.12 \u043f\u0440\u0438\u043d\u044f\u0442\u0430 \u043f\u043e\u0434\u0441\u0438\u0441\u0442\u0435\u043c\u0430 KFence \u0434\u043b\u044f \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0438\u044f \u043e\u0448\u0438\u0431\u043e\u043a \u043f\u0440\u0438 \u0440\u0430\u0431\u043e\u0442\u0435 \u0441 \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, 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