In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
tick\/broadcast: Plug clockevents replacement race<\/p>\n
\u6731\u607a\u4e7e reported and decoded the following race condition when a broadcast
\ndevice is replaced:<\/p>\n
CPUA\t\t\t\t\tCPUB
\n __tick_broadcast_oneshot_control()
\n bc = tick_broadcast_device.evtdev;
\n\t\t\t\t\ttick_install_broadcast_device(dev)
\n \t\t\t\tclockevents_exchange_device(cur, dev)
\n\t\t\t\t\t shutdown(cur);
\n\t\t\t\t\t detach(cur);
\n\t\t\t\t\t cur->handler = noop;
\n\t\t\t\t\t tick_broadcast_device.evtdev = dev;<\/p>\n
tick_broadcast_set_event(bc, next_event); <- FAIL: arms a detached device.<\/p>\n
If the original broadcast device has a restricted interrupt affinity mask
\nand the last CPU in that mask goes offline then the BUG() in
\ntick_cleanup_dead_cpu() triggers because the clockevent device is not in
\ndetached state.<\/p>\n
The reason for this is that tick_install_broadcast_device() is not
\nserialized vs. tick broadcast operations.<\/p>\n
The obvious cure is to serialize tick_install_broadcast_device() with
\ntick_broadcast_lock against a concurrent tick broadcast operation.<\/p>\n
That requires to split clockevents_exchange_device() into two parts, one
\nwhich does the exchange, shutdown and detach operation and the other which
\ndrops the module reference count. This is required because the module
\nreference cannot be dropped while holding tick_broadcast_lock.<\/p>\n
Let clockevents_exchange_device() do both operations as before, but let the
\nbroadcast device code take the two step approach and do the device
\nexchange under tick_broadcast_lock and drop the module reference count
\nafter releasing it.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
tick\/broadcast: Plug clockevents replacement race<\/p>\n
\u6731\u607a\u4e7e reported and decoded the following race condition when a broadcast
\ndevice is<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-29081","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/29081","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=29081"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=29081"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=29081"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}