From d1f76dfadaf8f47ed1753f97dbcbd41c16215ffa Mon Sep 17 00:00:00 2001 From: Xin Long Date: Mon, 17 May 2021 02:28:58 +0800 Subject: [PATCH] tipc: wait and exit until all work queues are done commit 04c26faa51d1e2fe71cf13c45791f5174c37f986 upstream. On some host, a crash could be triggered simply by repeating these commands several times: # modprobe tipc # tipc bearer enable media udp name UDP1 localip 127.0.0.1 # rmmod tipc [] BUG: unable to handle kernel paging request at ffffffffc096bb00 [] Workqueue: events 0xffffffffc096bb00 [] Call Trace: [] ? process_one_work+0x1a7/0x360 [] ? worker_thread+0x30/0x390 [] ? create_worker+0x1a0/0x1a0 [] ? kthread+0x116/0x130 [] ? kthread_flush_work_fn+0x10/0x10 [] ? ret_from_fork+0x35/0x40 When removing the TIPC module, the UDP tunnel sock will be delayed to release in a work queue as sock_release() can't be done in rtnl_lock(). If the work queue is schedule to run after the TIPC module is removed, kernel will crash as the work queue function cleanup_beareri() code no longer exists when trying to invoke it. To fix it, this patch introduce a member wq_count in tipc_net to track the numbers of work queues in schedule, and wait and exit until all work queues are done in tipc_exit_net(). Fixes: d0f91938bede ("tipc: add ip/udp media type") Reported-by: Shuang Li Signed-off-by: Xin Long Acked-by: Jon Maloy Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/tipc/core.c | 3 +++ net/tipc/core.h | 2 ++ net/tipc/udp_media.c | 2 ++ 3 files changed, 7 insertions(+) diff --git a/net/tipc/core.c b/net/tipc/core.c index e3d79f8b69d8..90cf7e0bbaf0 100644 --- a/net/tipc/core.c +++ b/net/tipc/core.c @@ -107,6 +107,9 @@ static void __net_exit tipc_exit_net(struct net *net) tipc_bcast_stop(net); tipc_nametbl_stop(net); tipc_sk_rht_destroy(net); + + while (atomic_read(&tn->wq_count)) + cond_resched(); } static struct pernet_operations tipc_net_ops = { diff --git a/net/tipc/core.h b/net/tipc/core.h index e119c4a88d63..c6bda91f8581 100644 --- a/net/tipc/core.h +++ b/net/tipc/core.h @@ -143,6 +143,8 @@ struct tipc_net { /* Work item for net finalize */ struct tipc_net_work final_work; + /* The numbers of work queues in schedule */ + atomic_t wq_count; }; static inline struct tipc_net *tipc_net(struct net *net) diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c index 8f0977a9d423..1fb0535e2eb4 100644 --- a/net/tipc/udp_media.c +++ b/net/tipc/udp_media.c @@ -802,6 +802,7 @@ static void cleanup_bearer(struct work_struct *work) kfree_rcu(rcast, rcu); } + atomic_dec(&tipc_net(sock_net(ub->ubsock->sk))->wq_count); dst_cache_destroy(&ub->rcast.dst_cache); udp_tunnel_sock_release(ub->ubsock); synchronize_net(); @@ -822,6 +823,7 @@ static void tipc_udp_disable(struct tipc_bearer *b) RCU_INIT_POINTER(ub->bearer, NULL); /* sock_release need to be done outside of rtnl lock */ + atomic_inc(&tipc_net(sock_net(ub->ubsock->sk))->wq_count); INIT_WORK(&ub->work, cleanup_bearer); schedule_work(&ub->work); }