Ukuba sengozini (CVE-2021-4155) kukhonjwe kukhodi yesistimu yefayela ye-XFS evumela umsebenzisi wasendaweni ongenamalungelo ukuthi afunde idatha yebhulokhi engasetshenziswanga ngokuqondile kudivayisi evinjiwe. Zonke izinguqulo ezinkulu ze-Linux kernel ezindala kuno-5.16 eziqukethe umshayeli we-XFS ziyathinteka kulolu daba. Ukulungiswa kufakwe kunguqulo 5.16, kanye nezibuyekezo ze-kernel 5.15.14, 5.10.91, 5.4.171, 4.19.225, njll. Isimo sezibuyekezo ezikhiqizwayo ukuze kulungiswe inkinga ekusatshalalisweni singalandelelwa kulawa makhasi: I-Debian, RHEL, SUSE, Fedora, Ubuntu, Arch.
Ukuba sengozini kubangelwa ukuziphatha okungalungile kwe-XFS-specific ioctl(XFS_IOC_ALLOCSP) kanye ne-ioctl(XFS_IOC_FREESP), okuyi-analogue esebenzayo yekholi yesistimu ye-kernel-wide fallocate(). Uma ukhuphula usayizi wefayela ongaqondanisiwe, i-ioctls XFS_IOC_ALLOCSP/XFS_IOC_FREESP ingasethi kabusha amabhayithi omsila abe uziro kuze kube umngcele webhulokhi olandelayo. Ngakho, ku-XFS enosayizi webhulokhi ojwayelekile wamabhayithi angu-4096, umhlaseli angakwazi ukufunda amabhayithi angu-4095 wedatha ebhaliwe yangaphambilini kusuka kubhulokhi ngayinye. Lezi zindawo zingaqukatha idatha evela kumafayela asusiwe, amafayela ahlukanisiwe, namafayela anamabhulokhi akhishiwe.
Ungahlola isistimu yakho ngenkinga usebenzisa i-exploit prototype elula. Uma, ngemva kokwenza ukulandelana okuhlongozwayo kwemiyalo, kungenzeka ukufunda umbhalo kaShakespeare, khona-ke umshayeli we-FS usengozini. Ekuqaleni ukukhweza ukwahlukanisa kwe-XFS ukuze kuboniswe kudinga amalungelo ezimpande.
Njengoba i-ioctl(XFS_IOC_ALLOCSP) kanye ne-ioctl(XFS_IOC_FREESP) zifana ngokusebenza njenge-fallocate ejwayelekile(), futhi umehluko wazo kuphela ukuvuza kwedatha, ubukhona bazo bufana ne-backdoor. Ngaphandle kwenqubomgomo evamile yokungashintshi ukuxhumana okukhona ku-kernel, ngokusikisela kwe-Linus, kunqunywe ukuthi kususwe ngokuphelele lawa ma-ioctls enguqulweni elandelayo.
Source: opennet.ru