Messages in this thread | | | Subject | Re: [PATCH] exit: clear TIF_MEMDIE after exit_task_work | From | Tetsuo Handa <> | Date | Mon, 13 Jun 2016 22:52:43 +0900 |
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Michal Hocko wrote: > I have checked the vnet code and it doesn't seem to rely on > copy_from_user/get_user AFAICS. Other users of use_mm() need to copy to > the userspace only as well. So we should be perfectly safe to OOM reap > address space even when it is shared by the kthread [1] so this is > not really needed for the OOM correctness purpose. It would be much > nicer if the kthread didn't pin the mm for two long outside of the OOM > handling as well of course but that lowers the priority of the change. > > [1] http://lkml.kernel.org/r/20160613112348.GC6518@dhcp22.suse.cz
It seems to me that vhost code relies on copy from the userspace.
use_mm(dev->mm) and unuse_mm(dev->mm) are used inside vhost_worker(). work->fn(work) is initialized by vhost_work_init(). vhost_scsi_open() passes vhost_scsi_complete_cmd_work() and vhost_scsi_evt_work() as ->fn, and both functions call __get_user().
vhost_scsi_complete_cmd_work() { vhost_signal() { vhost_notify() { __get_user() } } }
vhost_scsi_evt_work() { vhost_scsi_do_evt_work() { vhost_get_vq_desc() { __get_user() / __copy_from_user() get_indirect() { copy_from_iter() } } } }
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