From: Vasily Averin <vvs@xxxxxxxxxxxxx> [ Upstream commit 81833de1a46edce9ca20cfe079872ac1c20ef359 ] restart_grace() uses hardcoded init_net. It can cause to "list_add double add" in following scenario: 1) nfsd and lockd was started in several net namespaces 2) nfsd in init_net was stopped (lockd was not stopped because it have users from another net namespaces) 3) lockd got signal, called restart_grace() -> set_grace_period() and enabled lock_manager in hardcoded init_net. 4) nfsd in init_net is started again, its lockd_up() calls set_grace_period() and tries to add lock_manager into init_net 2nd time. Jeff Layton suggest: "Make it safe to call locks_start_grace multiple times on the same lock_manager. If it's already on the global grace_list, then don't try to add it again. (But we don't intentionally add twice, so for now we WARN about that case.) With this change, we also need to ensure that the nfsd4 lock manager initializes the list before we call locks_start_grace. While we're at it, move the rest of the nfsd_net initialization into nfs4_state_create_net. I see no reason to have it spread over two functions like it is today." Suggested patch was updated to generate warning in described situation. Suggested-by: Jeff Layton <jlayton@xxxxxxxxxx> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> --- fs/nfs_common/grace.c | 6 +++++- fs/nfsd/nfs4state.c | 7 ++++--- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c index 1bd659938646..3b13fb3b0553 100644 --- a/fs/nfs_common/grace.c +++ b/fs/nfs_common/grace.c @@ -30,7 +30,11 @@ locks_start_grace(struct net *net, struct lock_manager *lm) struct list_head *grace_list = net_generic(net, grace_net_id); spin_lock(&grace_lock); - list_add(&lm->list, grace_list); + if (list_empty(&lm->list)) + list_add(&lm->list, grace_list); + else + WARN(1, "double list_add attempt detected in net %x %s\n", + net->ns.inum, (net == &init_net) ? "(init_net)" : ""); spin_unlock(&grace_lock); } EXPORT_SYMBOL_GPL(locks_start_grace); diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index cc74fb0dc02d..58764786091e 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7018,6 +7018,10 @@ static int nfs4_state_create_net(struct net *net) INIT_LIST_HEAD(&nn->sessionid_hashtbl[i]); nn->conf_name_tree = RB_ROOT; nn->unconf_name_tree = RB_ROOT; + nn->boot_time = get_seconds(); + nn->grace_ended = false; + nn->nfsd4_manager.block_opens = true; + INIT_LIST_HEAD(&nn->nfsd4_manager.list); INIT_LIST_HEAD(&nn->client_lru); INIT_LIST_HEAD(&nn->close_lru); INIT_LIST_HEAD(&nn->del_recall_lru); @@ -7075,9 +7079,6 @@ nfs4_state_start_net(struct net *net) ret = nfs4_state_create_net(net); if (ret) return ret; - nn->boot_time = get_seconds(); - nn->grace_ended = false; - nn->nfsd4_manager.block_opens = true; locks_start_grace(net, &nn->nfsd4_manager); nfsd4_client_tracking_init(net); printk(KERN_INFO "NFSD: starting %ld-second grace period (net %p)\n", -- 2.11.0