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To:     Kishon Vijay Abraham I <kishon@ti.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Vinod Koul <vkoul@kernel.org>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        Vignesh Raghavendra <vigneshr@ti.com>
Cc:     dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20210209090036.30832-1-kishon@ti.com>
From:   =?UTF-8?Q?P=c3=a9ter_Ujfalusi?= <peter.ujfalusi@gmail.com>
Subject: Re: [PATCH] dmaengine: ti: k3-udma: Fix NULL pointer dereference
 error
Message-ID: <19488154-22d5-33b4-06a1-17e9a896ae04@gmail.com>
Date:   Tue, 9 Feb 2021 14:23:23 +0200
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Hi Kishon,

On 2/9/21 11:00 AM, Kishon Vijay Abraham I wrote:
> bcdma_get_*() and udma_get_*() checks if bchan/rchan/tchan/rflow is
> already allocated by checking if it has a NON NULL value. For the
> error cases, bchan/rchan/tchan/rflow will have error value
> and bcdma_get_*() and udma_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/rchan/tchan/rflow.

I think this can happen when a channel request fails and we get a second
request coming and faces with the not cleanup up tchan/rchan/bchan/rflow
from the previous failure.
Interesting that I have not faced with this, but it is a valid oversight
from me.

> Reset the value of bchan/rchan/tchan/rflow to NULL if the allocation
> actually fails.
> 
> Fixes: 017794739702 ("dmaengine: ti: k3-udma: Initial support for K3 BCDMA")
> Fixes: 25dcb5dd7b7c ("dmaengine: ti: New driver for K3 UDMA")

Will this patch apply at any of these?
25dcb5dd7b7c does not have BCDMA (bchan)
017794739702 does not contain PKTDMA (tflow)

> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
>  drivers/dma/ti/k3-udma.c | 30 +++++++++++++++++++++++++-----
>  1 file changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> index 298460438bb4..aa4ef583ff83 100644
> --- a/drivers/dma/ti/k3-udma.c
> +++ b/drivers/dma/ti/k3-udma.c
> @@ -1330,6 +1330,7 @@ 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",
> @@ -1347,8 +1348,11 @@ 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;
>  
> @@ -1358,6 +1362,7 @@ static int bcdma_get_bchan(struct udma_chan *uc)
>  static int udma_get_tchan(struct udma_chan *uc)
>  {
>  	struct udma_dev *ud = uc->ud;
> +	int ret;
>  
>  	if (uc->tchan) {
>  		dev_dbg(ud->dev, "chan%d: already have tchan%d allocated\n",
> @@ -1372,8 +1377,11 @@ static int udma_get_tchan(struct udma_chan *uc)
>  	 */
>  	uc->tchan = __udma_reserve_tchan(ud, uc->config.channel_tpl,
>  					 uc->config.mapped_channel_id);
> -	if (IS_ERR(uc->tchan))
> -		return PTR_ERR(uc->tchan);
> +	if (IS_ERR(uc->tchan)) {
> +		ret = PTR_ERR(uc->tchan);
> +		uc->tchan = NULL;
> +		return ret;
> +	}
>  
>  	if (ud->tflow_cnt) {
>  		int tflow_id;
> @@ -1403,6 +1411,7 @@ static int udma_get_tchan(struct udma_chan *uc)
>  static int udma_get_rchan(struct udma_chan *uc)
>  {
>  	struct udma_dev *ud = uc->ud;
> +	int ret;
>  
>  	if (uc->rchan) {
>  		dev_dbg(ud->dev, "chan%d: already have rchan%d allocated\n",
> @@ -1417,8 +1426,13 @@ static int udma_get_rchan(struct udma_chan *uc)
>  	 */
>  	uc->rchan = __udma_reserve_rchan(ud, uc->config.channel_tpl,
>  					 uc->config.mapped_channel_id);
> +	if (IS_ERR(uc->rchan)) {
> +		ret = PTR_ERR(uc->rchan);
> +		uc->rchan = NULL;
> +		return ret;
> +	}
>  
> -	return PTR_ERR_OR_ZERO(uc->rchan);
> +	return 0;
>  }
>  
>  static int udma_get_chan_pair(struct udma_chan *uc)
> @@ -1472,6 +1486,7 @@ static int udma_get_chan_pair(struct udma_chan *uc)
>  static int udma_get_rflow(struct udma_chan *uc, int flow_id)
>  {
>  	struct udma_dev *ud = uc->ud;
> +	int ret;
>  
>  	if (!uc->rchan) {
>  		dev_err(ud->dev, "chan%d: does not have rchan??\n", uc->id);
> @@ -1485,6 +1500,11 @@ static int udma_get_rflow(struct udma_chan *uc, int flow_id)
>  	}
>  
>  	uc->rflow = __udma_get_rflow(ud, flow_id);
> +	if (IS_ERR(uc->rflow)) {
> +		ret = PTR_ERR(uc->rflow);
> +		uc->rflow = NULL;
> +		return ret;
> +	}
>  
>  	return PTR_ERR_OR_ZERO(uc->rflow);

return 0;

>  }
> 

-- 
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