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

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Message-ID: <a2a43d5a-678d-129b-d258-d559df42431f@redhat.com>
Date:   Mon, 2 Oct 2023 16:30:37 -0400
From:   Jon Maloy <jmaloy@...hat.com>
To:     Chengfeng Ye <dg573847474@...il.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 2023-09-27 14:14, 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.
>
> 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>
> ---
>   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;
Acked-by: Jon Maloy <jmaloy@...hat.com>