[PATCH 5.12 134/296] tipc: wait and exit until all work queues are done

Greg Kroah-Hartman
2021-05-31T16:29:10Z

From: Xin Long <lucien.xin@gmail.com>

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 <shuali@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/tipc/core.c | 2 ++
net/tipc/core.h | 2 ++
net/tipc/udp_media.c | 2 ++
3 files changed, 6 insertions(+)

--- a/net/tipc/core.c
+++ b/net/tipc/core.c
@@ -119,6 +119,8 @@ static void __net_exit tipc_exit_net(str
#ifdef CONFIG_TIPC_CRYPTO
tipc_crypto_stop(&tipc_net(net)->crypto_tx);
#endif
+ while (atomic_read(&tn->wq_count))
+ cond_resched();
}

static void __net_exit tipc_pernet_pre_exit(struct net *net)
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -149,6 +149,8 @@ struct tipc_net {
#endif
/* 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)
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -812,6 +812,7 @@ static void cleanup_bearer(struct work_s
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();
@@ -832,6 +833,7 @@ static void tipc_udp_disable(struct tipc
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);
}