netdev - Re: [PATCH] tipc: fix a potential deadlock on &tx->lock

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Date: Fri, 29 Sep 2023 11:29:50 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Chengfeng Ye <dg573847474@...il.com>, <jmaloy@...hat.com>,
	<ying.xue@...driver.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>
CC: <netdev@...r.kernel.org>, <tipc-discussion@...ts.sourceforge.net>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tipc: fix a potential deadlock on &tx->lock



On 9/27/2023 11:14 AM, Chengfeng Ye wrote:
> It seems that tipc_crypto_key_revoke() could be be invoked by
> wokequeue tipc_crypto_work_rx() under process context and
> timer/rx callback under softirq context, thus the lock acquisition
> on &tx->lock seems better use spin_lock_bh() to prevent possible
> deadlock.
> 
> This flaw was found by an experimental static analysis tool I am
> developing for irq-related deadlock.
> 

Interesting.

> tipc_crypto_work_rx() <workqueue>
> --> tipc_crypto_key_distr()
> --> tipc_bcast_xmit()
> --> tipc_bcbase_xmit()
> --> tipc_bearer_bc_xmit()
> --> tipc_crypto_xmit()
> --> tipc_ehdr_build()
> --> tipc_crypto_key_revoke()
> --> spin_lock(&tx->lock)
> <timer interrupt>
>    --> tipc_disc_timeout()
>    --> tipc_bearer_xmit_skb()
>    --> tipc_crypto_xmit()
>    --> tipc_ehdr_build()
>    --> tipc_crypto_key_revoke()
>    --> spin_lock(&tx->lock) <deadlock here>
> 
> Signed-off-by: Chengfeng Ye <dg573847474@...il.com>
> ---

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

>  net/tipc/crypto.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
> index 302fd749c424..43c3f1c971b8 100644
> --- a/net/tipc/crypto.c
> +++ b/net/tipc/crypto.c
> @@ -1441,14 +1441,14 @@ static int tipc_crypto_key_revoke(struct net *net, u8 tx_key)
>  	struct tipc_crypto *tx = tipc_net(net)->crypto_tx;
>  	struct tipc_key key;
>  
> -	spin_lock(&tx->lock);
> +	spin_lock_bh(&tx->lock);
>  	key = tx->key;
>  	WARN_ON(!key.active || tx_key != key.active);
>  
>  	/* Free the active key */
>  	tipc_crypto_key_set_state(tx, key.passive, 0, key.pending);
>  	tipc_crypto_key_detach(tx->aead[key.active], &tx->lock);
> -	spin_unlock(&tx->lock);
> +	spin_unlock_bh(&tx->lock);
>  
>  	pr_warn("%s: key is revoked\n", tx->name);
>  	return -EKEYREVOKED;