netdev - Re: [PATCH net] tipc: change to check tipc_own_id to return in tipc_net

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Date:   Sun, 24 Mar 2019 15:32:55 +0800
From:   Ying Xue <ying.xue@...driver.com>
To:     Xin Long <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>
CC:     <davem@...emloft.net>, Jon Maloy <jon.maloy@...csson.com>,
        <tipc-discussion@...ts.sourceforge.net>,
        <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] tipc: change to check tipc_own_id to return in
 tipc_net_stop

On 3/24/19 12:48 AM, Xin Long wrote:
> When running a syz script, a panic occurred:
> 
> [  156.088228] BUG: KASAN: use-after-free in tipc_disc_timeout+0x9c9/0xb20 [tipc]
> [  156.094315] Call Trace:
> [  156.094844]  <IRQ>
> [  156.095306]  dump_stack+0x7c/0xc0
> [  156.097346]  print_address_description+0x65/0x22e
> [  156.100445]  kasan_report.cold.3+0x37/0x7a
> [  156.102402]  tipc_disc_timeout+0x9c9/0xb20 [tipc]
> [  156.106517]  call_timer_fn+0x19a/0x610
> [  156.112749]  run_timer_softirq+0xb51/0x1090
> 
> It was caused by the netns freed without deleting the discoverer timer,
> while later on the netns would be accessed in the timer handler.
> 
> The timer should have been deleted by tipc_net_stop() when cleaning up a
> netns. However, tipc has been able to enable a bearer and start d->timer
> without the local node_addr set since Commit 52dfae5c85a4 ("tipc: obtain
> node identity from interface by default"), which caused the timer not to
> be deleted in tipc_net_stop() then.
> 
> So fix it in tipc_net_stop() by changing to check local node_id instead
> of local node_addr, as Jon suggested.
> 
> While at it, remove the calling of tipc_nametbl_withdraw() there, since
> tipc_nametbl_stop() will take of the nametbl's freeing after.
> 
> Fixes: 52dfae5c85a4 ("tipc: obtain node identity from interface by default")
> Reported-by: syzbot+a25307ad099309f1c2b9@...kaller.appspotmail.com
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Acked-by: Ying Xue <ying.xue@...driver.com>

> ---
>  net/tipc/net.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/net/tipc/net.c b/net/tipc/net.c
> index f076edb..7ce1e86 100644
> --- a/net/tipc/net.c
> +++ b/net/tipc/net.c
> @@ -163,12 +163,9 @@ void tipc_sched_net_finalize(struct net *net, u32 addr)
>  
>  void tipc_net_stop(struct net *net)
>  {
> -	u32 self = tipc_own_addr(net);
> -
> -	if (!self)
> +	if (!tipc_own_id(net))
>  		return;
>  
> -	tipc_nametbl_withdraw(net, TIPC_CFG_SRV, self, self, self);
>  	rtnl_lock();
>  	tipc_bearer_stop(net);
>  	tipc_node_stop(net);
>