Sorry, this one is bad as well.
07.11.2017 11:28, Stanislav Kinsburskiy пишет: > Here is the race: > > CPU #0 CPU#1 > > cleanup_mnt nfs41_callback_svc (get xprt from the list) > nfs_callback_down ... > ... ... > svc_close_net ... > ... ... > svc_xprt_free ... > svc_bc_sock_free bc_svc_process > kfree(xprt) svc_process_common > rqstp->rq_xprt->xpt_ops (use after free) > > The problem is that per-net SUNRPC transports shutdown is done regardless > current callback execution. This is a race leading to transport use-after-free > in callback handler. > This patch fixes it in stright-forward way. I.e. it protects callback > execution with the same mutex used for per-net data creation and destruction. > Hopefully, it won't slow down NFS client significantly. > > https://jira.sw.ru/browse/PSBM-75751 > > v2: Fix mutex deadlock, when shutdown callback waits for thread to exit (with > mutex taken), while thread wait for the mutex to take. > > Signed-off-by: Stanislav Kinsburskiy <skinsbur...@virtuozzo.com> > --- > fs/nfs/callback.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c > index 0beb275..eed861a 100644 > --- a/fs/nfs/callback.c > +++ b/fs/nfs/callback.c > @@ -118,6 +118,11 @@ nfs41_callback_svc(void *vrqstp) > continue; > > prepare_to_wait(&serv->sv_cb_waitq, &wq, TASK_INTERRUPTIBLE); > + > + if (!mutex_trylock(&nfs_callback_mutex) && > + kthread_should_stop()) > + return 0; > + > spin_lock_bh(&serv->sv_cb_lock); > if (!list_empty(&serv->sv_cb_list)) { > req = list_first_entry(&serv->sv_cb_list, > @@ -129,8 +134,10 @@ nfs41_callback_svc(void *vrqstp) > error = bc_svc_process(serv, req, rqstp); > dprintk("bc_svc_process() returned w/ error code= %d\n", > error); > + mutex_unlock(&nfs_callback_mutex); > } else { > spin_unlock_bh(&serv->sv_cb_lock); > + mutex_unlock(&nfs_callback_mutex); > schedule(); > finish_wait(&serv->sv_cb_waitq, &wq); > } > > _______________________________________________ > Devel mailing list > Devel@openvz.org > https://lists.openvz.org/mailman/listinfo/devel > _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel