netdev - RE: [PATCH net-next] tipc: don't call sock

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Message-ID: <BN6PR15MB1553D3AD819F704566D2CA6A9AC80@BN6PR15MB1553.namprd15.prod.outlook.com>
Date:   Mon, 19 Feb 2018 18:53:50 +0000
From:   Jon Maloy <jon.maloy@...csson.com>
To:     Paolo Abeni <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     Ying Xue <ying.xue@...driver.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: RE: [PATCH net-next] tipc: don't call sock_release() in atomic
 context



> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-
> owner@...r.kernel.org] On Behalf Of Paolo Abeni
> Sent: Monday, February 19, 2018 19:02
> To: netdev@...r.kernel.org
> Cc: Jon Maloy <jon.maloy@...csson.com>; Ying Xue
> <ying.xue@...driver.com>; David S. Miller <davem@...emloft.net>
> Subject: [PATCH net-next] tipc: don't call sock_release() in atomic context
> 
> syzbot reported a scheduling while atomic issue at netns destruction time:
> 
> BUG: sleeping function called from invalid context at net/core/sock.c:2769
> in_atomic(): 1, irqs_disabled(): 0, pid: 85, name: kworker/u4:3
> 5 locks held by kworker/u4:3/85:
>   #0:  ((wq_completion)"%s""netns"){+.+.}, at: [<00000000c9792deb>]
> process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084
>   #1:  (net_cleanup_work){+.+.}, at: [<00000000adc12e2a>]
> process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088
>   #2:  (net_sem){++++}, at: [<000000009ccb5669>] cleanup_net+0x23f/0xd20
> net/core/net_namespace.c:494
>   #3:  (net_mutex){+.+.}, at: [<00000000a92767d9>]
> cleanup_net+0xa7d/0xd20
> net/core/net_namespace.c:496
>   #4:  (&(&srv->idr_lock)->rlock){+...}, at: [<000000001343e568>]
> spin_lock_bh include/linux/spinlock.h:315 [inline]
>   #4:  (&(&srv->idr_lock)->rlock){+...}, at: [<000000001343e568>]
> tipc_topsrv_stop+0x231/0x610 net/tipc/topsrv.c:685
> CPU: 0 PID: 85 Comm: kworker/u4:3 Not tainted 4.16.0-rc1+ #230 Hardware
> name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: netns cleanup_net
> Call Trace:
>   __dump_stack lib/dump_stack.c:17 [inline]
>   dump_stack+0x194/0x257 lib/dump_stack.c:53
>   ___might_sleep+0x2b2/0x470 kernel/sched/core.c:6128
>   __might_sleep+0x95/0x190 kernel/sched/core.c:6081
>   lock_sock_nested+0x37/0x110 net/core/sock.c:2769
>   lock_sock include/net/sock.h:1463 [inline]
>   tipc_release+0x103/0xff0 net/tipc/socket.c:572
>   sock_release+0x8d/0x1e0 net/socket.c:594
>   tipc_topsrv_stop+0x3c0/0x610 net/tipc/topsrv.c:696
>   tipc_exit_net+0x15/0x40 net/tipc/core.c:96
>   ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:148
>   cleanup_net+0x6ba/0xd20 net/core/net_namespace.c:529
>   process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
>   worker_thread+0x223/0x1990 kernel/workqueue.c:2247
>   kthread+0x33c/0x400 kernel/kthread.c:238
>   ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:429
> 
> This is caused by tipc_topsrv_stop() releasing the listener socket with the idr
> lock held. This changeset addresses the issue moving the release operation
> outside such lock.

Thank you Paolo. This was too obvious for me to catch ☹
Acked-by:  ///jon

> 
> Reported-and-tested-by:
> syzbot+749d9d87c294c00ca856@...kaller.appspotmail.com
> Fixes: 0ef897be12b8 ("tipc: separate topology server listener socket from
> subcsriber sockets")
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
>  net/tipc/topsrv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c index
> 02013e00f287..63f35eae7236 100644
> --- a/net/tipc/topsrv.c
> +++ b/net/tipc/topsrv.c
> @@ -693,9 +693,9 @@ void tipc_topsrv_stop(struct net *net)
>  	}
>  	__module_get(lsock->ops->owner);
>  	__module_get(lsock->sk->sk_prot_creator->owner);
> -	sock_release(lsock);
>  	srv->listener = NULL;
>  	spin_unlock_bh(&srv->idr_lock);
> +	sock_release(lsock);
>  	tipc_topsrv_work_stop(srv);
>  	idr_destroy(&srv->conn_idr);
>  	kfree(srv);
> --
> 2.14.3