linux-kernel - Re: [PATCH] ata: dwc_460ex: Avoid potential NULL pointer dereference

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Message-ID: <66403341-fa27-4b80-ab6b-2413b6b6fb98@kernel.dk>
Date:   Sun, 24 Mar 2019 10:28:23 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Aditya Pakki <pakki001@....edu>
Cc:     kjlu@....edu, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: dwc_460ex: Avoid potential NULL pointer dereference

On 3/4/19 4:08 PM, Aditya Pakki wrote:
> dma_async_tx_descriptor can contain a NULL variable and using
> it in dmaengine_submit without checking can crash the process.
> This patch avoids such a scenario.
> 
> Signed-off-by: Aditya Pakki <pakki001@....edu>
> ---
>  drivers/ata/sata_dwc_460ex.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
> index 6f142aa54f5f..44a0d7a1ef54 100644
> --- a/drivers/ata/sata_dwc_460ex.c
> +++ b/drivers/ata/sata_dwc_460ex.c
> @@ -1052,8 +1052,10 @@ static void sata_dwc_bmdma_start_by_tag(struct ata_queued_cmd *qc, u8 tag)
>  					SATA_DWC_DMACR_RXCHEN);
>  
>  		/* Enable AHB DMA transfer on the specified channel */
> -		dmaengine_submit(desc);
> -		dma_async_issue_pending(hsdevp->chan);
> +		if (desc) {
> +			dmaengine_submit(desc);
> +			dma_async_issue_pending(hsdevp->chan);
> +		}
>  	}
>  }

Hmm, if desc == NULL, is that an error condition?

-- 
Jens Axboe