In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes<\/p>\n
cleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes
\nper call and is called again until the dying wb is drained, but every
\ncall walks wb->b_attached and then wb->b_dirty_time from the same end.
\nInodes already prepared (they stay on the list with I_WB_SWITCH set
\nuntil the switch worker runs) and inodes that cannot be switched
\n(I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb)
\nstay where they are, so each pass rescans a growing run of them under
\nwb->list_lock and a full drain is quadratic in the number of inodes on
\nthe list. With ~17M inodes attached to one dying cgwb we saw this end
\nin soft lockups, with CPUs reported stuck for 21-48s.<\/p>\n
Walk both lists from the oldest end and move every scanned inode to
\nthe newest end, so the next pass starts where the previous one stopped
\nand the drain becomes linear. b_attached is unordered, so nobody sees
\nthe reorder there. b_dirty_time is ordered by dirtied_when, but the
\noldest unscanned inode stays at the end move_expired_inodes() picks
\nfrom, sync takes the whole list regardless of order, and prepared
\ninodes leave the list as soon as the switch work runs and get a new
\ndirtied_time_when on the new wb anyway, so the only inodes left out of
\norder are the ones that can never switch (DAX), and only on the dying
\nwb.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes<\/p>\n
cleanup_offline_cgwb() prepares at most WB_MAX_INODES_P<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-41010","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/41010","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41010"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41010"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41010"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}