linux-kernel - Re: [PATCH 1/2] dmaengine: ti: k3-udma: Fix NULL pointer dereference error for BCDMA

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Date:   Wed, 27 Oct 2021 11:24:52 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Vinod Koul <vkoul@...nel.org>
CC:     <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [PATCH 1/2] dmaengine: ti: k3-udma: Fix NULL pointer dereference
 error for BCDMA

Hi All,

On 27/10/21 11:22 am, Kishon Vijay Abraham I wrote:
> bcdma_get_*() checks if bchan is already allocated by checking if it
> has a NON NULL value. For the error cases, bchan will have error value
> and bcdma_get_*() considers this as already allocated (PASS) since the
> error values are NON NULL. This results in NULL pointer dereference
> error while de-referencing bchan.
> 
> Reset the value of bchan to NULL if the allocation actually fails.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>

Please ignore this series. There was some stray patches left which I failed to
notice before sending. I'll resend a clean one.


Thanks,
Kishon
> ---
>  drivers/dma/ti/k3-udma.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> index a35858610780..14ae28830871 100644
> --- a/drivers/dma/ti/k3-udma.c
> +++ b/drivers/dma/ti/k3-udma.c
> @@ -1348,6 +1348,7 @@ static int bcdma_get_bchan(struct udma_chan *uc)
>  {
>  	struct udma_dev *ud = uc->ud;
>  	enum udma_tp_level tpl;
> +	int ret;
>  
>  	if (uc->bchan) {
>  		dev_dbg(ud->dev, "chan%d: already have bchan%d allocated\n",
> @@ -1365,8 +1366,11 @@ static int bcdma_get_bchan(struct udma_chan *uc)
>  		tpl = ud->bchan_tpl.levels - 1;
>  
>  	uc->bchan = __udma_reserve_bchan(ud, tpl, -1);
> -	if (IS_ERR(uc->bchan))
> -		return PTR_ERR(uc->bchan);
> +	if (IS_ERR(uc->bchan)) {
> +		ret = PTR_ERR(uc->bchan);
> +		uc->bchan = NULL;
> +		return ret;
> +	}
>  
>  	uc->tchan = uc->bchan;
>  
>