Kusagadzikana (CVE-2021-4155) yakaonekwa muXFS faira system kodhi inobvumira mushandisi wemuno asina rusaruro kuti averenge isina kushandiswa block data zvakananga kubva kune block mudziyo. Ese mavhezheni makuru eLinux kernel akakura kupfuura 5.16 ane mutyairi weXFS anokanganiswa nenyaya iyi. Kugadziriswa kwaisanganisira muvhezheni 5.16, pamwe nekuvandudza kernel 5.15.14, 5.10.91, 5.4.171, 4.19.225, nezvimwe. Mamiriro ekugadzirisa ari kugadzirwa kugadzirisa dambudziko mukugovera anogona kuteverwa pamapeji aya: Debian, RHEL, SUSE, Fedora, Ubuntu, Arch.
Kusagadzikana kunokonzerwa nemaitiro asiri iwo maviri eXFS-specific ioctl(XFS_IOC_ALLOCSP) uye ioctl(XFS_IOC_FREESP), inova analogue inoshanda yekernel-wide fallocate() system call. Paunenge uchiwedzera saizi yefaira isina kuvharika-yakaiswa, ioctls XFS_IOC_ALLOCSP/XFS_IOC_FREESP usadzore mabheti emuswe kusvika zero kusvika pamuganhu unotevera. Saka, paXFS ine chiyero che block block ye4096 bytes, munhu anorwisa anogona kuverenga kusvika ku4095 bytes ye data rakanyorwa rakapfuura kubva kubhuroka rega rega. Idzi nzvimbo dzinogona kunge dziine data kubva kune akadzimwa mafaera, akacheneswa mafaera, uye mafaera ane deduplicated blocks.
Unogona kuyedza system yako yedambudziko uchishandisa yakapusa prototype. Kana, mushure mekuita kutevedzana kwakarongwa kwemirairo, zvinokwanisika kuverenga chinyorwa chaShakespeare, ipapo mutyairi weFS ari panjodzi. Pakutanga kukwidza chikamu cheXFS chekuratidzira kunoda maropafadzo emidzi.
Sezvo ioctl(XFS_IOC_ALLOCSP) uye ioctl(XFS_IOC_FREESP) zvakangofanana mukushanda seyakajairwa fallocate(), uye mutsauko wavo chete ndeyekudonha kwedata, kuvapo kwavo kwakafanana nebackdoor. Kunyangwe mutemo wakajairika wekusachinja maficha aripo mukernel, pane zano reLinus, zvakasarudzwa kubvisa zvachose aya maoctls mune inotevera vhezheni.
Source: opennet.ru