{"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\/pl\/blog\/news\/v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu","title":{"rendered":"Substystem KFence do wykrywania b\u0142\u0119d\u00f3w w pami\u0119ci przyj\u0119ty do j\u0105dra Linux 5.12","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Do rozwijanego j\u0105dra Linux 5.12 w\u0142\u0105czono implementacj\u0119 mechanizmu KFence (Kernel Electric Fence), kt\u00f3ry kontroluje operacje na pami\u0119ci, wykrywaj\u0105c przekroczenia granic bufor\u00f3w, odwo\u0142ania do pami\u0119ci po jej zwolnieniu oraz inne b\u0142\u0119dy tego typu. <\/p>\n

Podobna funkcjonalno\u015b\u0107 by\u0142a ju\u017c obecna w j\u0105drze w postaci opcji kompilacji KASAN (kernel address sanitizer, wykorzystuj\u0105cy Address Sanitizer w nowoczesnych gcc i clang) \u2014 jednak by\u0142a g\u0142\u00f3wnie pozycjonowana do zastosowa\u0144 debuguj\u0105cych. Podsystem KFence r\u00f3\u017cni si\u0119 od KASAN wysok\u0105 szybko\u015bci\u0105 dzia\u0142ania, co pozwala na stosowanie tej funkcji nawet w j\u0105drze dzia\u0142aj\u0105cych system\u00f3w. <\/p>\n

Zastosowanie w systemach produkcyjnych pozwoli wykrywa\u0107 b\u0142\u0119dy operacji na pami\u0119ci, kt\u00f3re nie ujawniaj\u0105 si\u0119 podczas test\u00f3w i wychodz\u0105 na jaw dopiero pod rzeczywistym obci\u0105\u017ceniem lub przy d\u0142ugim czasie pracy systemu (du\u017cym uptime). Ponadto u\u017cycie KFence w systemach produkcyjnych pozwoli znacz\u0105co zwi\u0119kszy\u0107 liczb\u0119 maszyn uczestnicz\u0105cych w weryfikacji dzia\u0142ania j\u0105dra pod k\u0105tem obs\u0142ugi pami\u0119ci. <\/p>\n

Minimalny narzut, niezale\u017cny od obci\u0105\u017cenia, KFence osi\u0105ga dzi\u0119ki wstawianiu stron ochronnych (guard pages) do sterty w sta\u0142ych odst\u0119pach. Po up\u0142ywie kolejnego interwa\u0142u ochrony KFence, za po\u015brednictwem standardowego systemu przydzia\u0142u pami\u0119ci (alokatora SLAB lub SLUB), dodaje nast\u0119pn\u0105 stron\u0119 ochronn\u0105 z puli obiekt\u00f3w KFence i rozpoczyna nowy pomiar czasu. Ka\u017cdy obiekt KFence jest umieszczany na osobnej stronie pami\u0119ci, a strony po lewej i prawej stronie tworz\u0105 strony ochronne (guard pages), kt\u00f3rych rozmiar jest dobierany losowo. <\/p>\n

W ten spos\u00f3b strony z obiektami s\u0105 oddzielane od siebie stronami ochronnymi, kt\u00f3re s\u0105 konfigurowane do generowania \u201epage fault\u201d przy jakimkolwiek odwo\u0142aniu. Aby zidentyfikowa\u0107 operacje zapisu poza granice bufora w stronach z obiektami, dodatkowo wykorzystuje si\u0119 \u201eczerwone strefy\u201d na podstawie wzorc\u00f3w, kt\u00f3re zajmuj\u0105 pami\u0119\u0107 niewykorzystan\u0105 przez obiekty, pozostaj\u0105c\u0105 przy wyr\u00f3wnywaniu rozmiaru stron pami\u0119ci. \u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+ | 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 | \u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+\u2014\u2014+ <\/p>\n

W przypadku pr\u00f3by odwo\u0142ania si\u0119 do obszaru poza granicami bufora operacja dotyka strony ochronnej, co prowadzi do wygenerowania \u201epage fault\u201d, kt\u00f3re przechwytuje KFence i zapisuje w logu dane o wykrytym problemie. Domy\u015blnie KFence nie blokuje b\u0142\u0119du i jedynie wy\u015bwietla ostrze\u017cenie w logu, ale przewidziano konfiguracj\u0119 \u201epanic_on_warn\u201d, kt\u00f3ra pozwala w przypadku wykrycia b\u0142\u0119du przekszta\u0142ci\u0107 j\u0105dro w stan awarii (panic).
\n
\u0179r\u00f3d\u0142o: 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\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\u0105dra Linux 5.12 trafi\u0142 podsystem KFence do wykrywania b\u0142\u0119d\u00f3w w pracy z pami\u0119ci\u0105 | ProHoster","description":"Do rozwijanego j\u0105dra Linux 5.12 w\u0142\u0105czono implementacj\u0119 mechanizmu KFence (Kernel Electric Fence), kt\u00f3ry kontroluje prac\u0119 z pami\u0119ci\u0105, wykrywaj\u0105c wyj\u015bcia poza granice bufor\u00f3w oraz odwo\u0142ania do pami\u0119ci 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