linux-kernel - Re: [PATCH 4.4 04/35] iwlwifi: pcie: add a NULL check in iwl_pcie_txq

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Date:   Thu, 25 Feb 2021 15:04:46 +0900
From:   Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.4 04/35] iwlwifi: pcie: add a NULL check in
 iwl_pcie_txq_unmap

Hi,

Sorry for the report after the release.

On Mon, Feb 22, 2021 at 01:36:00PM +0100, Greg Kroah-Hartman wrote:
> From: Emmanuel Grumbach <emmanuel.grumbach@...el.com>
> 
> [ Upstream commit 98c7d21f957b10d9c07a3a60a3a5a8f326a197e5 ]
> 
> I hit a NULL pointer exception in this function when the
> init flow went really bad.
> 
> Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@...el.com>
> Signed-off-by: Luca Coelho <luciano.coelho@...el.com>
> Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
> Link: https://lore.kernel.org/r/iwlwifi.20210115130252.2e8da9f2c132.I0234d4b8ddaf70aaa5028a20c863255e05bc1f84@changeid
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/net/wireless/iwlwifi/pcie/tx.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/wireless/iwlwifi/pcie/tx.c b/drivers/net/wireless/iwlwifi/pcie/tx.c
> index 8dfe6b2bc7031..cb03c2855019b 100644
> --- a/drivers/net/wireless/iwlwifi/pcie/tx.c
> +++ b/drivers/net/wireless/iwlwifi/pcie/tx.c
> @@ -585,6 +585,11 @@ static void iwl_pcie_txq_unmap(struct iwl_trans *trans, int txq_id)
>  	struct iwl_txq *txq = &trans_pcie->txq[txq_id];
>  	struct iwl_queue *q = &txq->q;
>  
> +	if (!txq) {
> +		IWL_ERR(trans, "Trying to free a queue that wasn't allocated?\n");
> +		return;
> +	}
> +

I think that this fix is not enough.
If txq is NULL, an error will occur with "struct iwl_queue * q = & txq->q;".
The following changes are required.

diff --git a/drivers/net/wireless/iwlwifi/pcie/tx.c b/drivers/net/wireless/iwlwifi/pcie/tx.c
index cb03c2855019b7..7584796131fa41 100644
--- a/drivers/net/wireless/iwlwifi/pcie/tx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/tx.c
@@ -583,13 +583,15 @@ static void iwl_pcie_txq_unmap(struct iwl_trans *trans, int txq_id)
 {
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 	struct iwl_txq *txq = &trans_pcie->txq[txq_id];
-	struct iwl_queue *q = &txq->q;
+	struct iwl_queue *q;
 
 	if (!txq) {
 		IWL_ERR(trans, "Trying to free a queue that wasn't allocated?\n");
 		return;
 	}
 
+	q = &txq->q;
+
 	spin_lock_bh(&txq->lock);
 	while (q->write_ptr != q->read_ptr) {
 		IWL_DEBUG_TX_REPLY(trans, "Q %d Free %d\n",



>  	spin_lock_bh(&txq->lock);
>  	while (q->write_ptr != q->read_ptr) {
>  		IWL_DEBUG_TX_REPLY(trans, "Q %d Free %d\n",
> -- 
> 2.27.0
> 
> 

Best regards,
  Nobuhiro