This is a note to let you know that I've just added the patch titled

lockd: fix "list_add double add" caused by legacy signal interface

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: lockd-fix-list_add-double-add-caused-by-legacy-signal-interface.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Feb 1 13:45:42 CET 2018

From: Vasily Averin vvs@virtuozzo.com Date: Mon, 13 Nov 2017 07:25:40 +0300 Subject: lockd: fix "list_add double add" caused by legacy signal interface

From: Vasily Averin vvs@virtuozzo.com

[ 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@redhat.com Signed-off-by: Vasily Averin vvs@virtuozzo.com Signed-off-by: J. Bruce Fields bfields@redhat.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/nfs_common/grace.c | 6 +++++- fs/nfsd/nfs4state.c | 7 ++++--- 2 files changed, 9 insertions(+), 4 deletions(-)

--- a/fs/nfs_common/grace.c +++ b/fs/nfs_common/grace.c @@ -30,7 +30,11 @@ locks_start_grace(struct net *net, struc 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); --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7021,6 +7021,10 @@ static int nfs4_state_create_net(struct 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); @@ -7078,9 +7082,6 @@ 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",

Patches currently in stable-queue which might be from vvs@virtuozzo.com are

queue-4.14/lockd-fix-list_add-double-add-caused-by-legacy-signal-interface.patch queue-4.14/grace-replace-bug_on-by-warn_once-in-exit_net-hook.patch queue-4.14/perf-core-fix-memory-leak-triggered-by-perf-namespace.patch queue-4.14/race-of-lockd-inetaddr-notifiers-vs-nlmsvc_rqst-change.patch