In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
sched\/psi: Shut down rtpoll_timer in psi_cgroup_free()<\/p>\n
psi_schedule_rtpoll_work() is called locklessly from the scheduler hotpath
\nand can race psi_trigger_destroy() taking down the last rtpoll trigger under
\nrtpoll_trigger_lock:<\/p>\n
psi_schedule_rtpoll_work() psi_trigger_destroy()<\/p>\n
rcu_read_lock();
\n task = rcu_dereference(rtpoll_task);
\n rcu_assign_pointer(rtpoll_task, NULL);
\n timer_delete(&rtpoll_timer);
\n mod_timer(&rtpoll_timer, …);
\n rcu_read_unlock();
\n synchronize_rcu();
\n kthread_stop(task_to_destroy);<\/p>\n
The group can then be freed with the re-armed timer still pending, and
\npoll_timer_fn() runs on freed memory.<\/p>\n
461daba06bdc (“psi: eliminate kthread_worker from psi trigger scheduling
\nmechanism”) deleted the timer synchronously after the synchronize_rcu(),
\nwhich prevented this but raced trigger creation instead: the deletion could
\ncancel the timer that a new trigger set armed during the grace period and,
\nas creation also reinitialized the timer at the time, corrupt it.
\n8f91efd870ea (“psi: Fix race between psi_trigger_create\/destroy”) moved the
\ninitialization into group_init() and the deletion into the locked section,
\ntrading the creation races for the window above.<\/p>\n
Neither placement in the destruction path works. A pending timer firing
\nwhile the group is alive is harmless though. poll_timer_fn() just wakes the
\nrtpoll waitqueue and doesn’t re-arm itself. Bind the timer to the group’s
\nlifetime instead and shut it down in psi_cgroup_free(). Nothing can arm it
\nby then. timer_shutdown_sync() because the timer is never armed again.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
sched\/psi: Shut down rtpoll_timer in psi_cgroup_free()<\/p>\n
psi_schedule_rtpoll_work() is called locklessly from the scheduler hotpath<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-11204","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/11204","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=11204"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11204"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11204"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}