[PATCH v5 01/17] dmaengine: sh: rz-dmac: Move interrupt request after everything is set up

[PATCH v5 01/17] dmaengine: sh: rz-dmac: Move interrupt request after everything is set up

[Claudiu Beznea]

Once the interrupt is requested, the interrupt handler may run immediately.
Since the IRQ handler can access channel->ch_base, which is initialized
only after requesting the IRQ, this may lead to invalid memory access.
Likewise, the IRQ thread may access uninitialized data (the ld_free,
ld_queue, and ld_active lists), which may also lead to issues.

Request the interrupts only after everything is set up. To keep the error
path simpler, use dmam_alloc_coherent() instead of dma_alloc_coherent().

Fixes: 5000d37042a6 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Cc: stable@vger.kernel.org
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
---

Changes in v5:
- none

Changes in v4:
- none, this patch is new

 drivers/dma/sh/rz-dmac.c | 88 +++++++++++++++-------------------------
 1 file changed, 33 insertions(+), 55 deletions(-)

diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
index 625ff29024de..9f206a33dcc6 100644
--- a/drivers/dma/sh/rz-dmac.c
+++ b/drivers/dma/sh/rz-dmac.c
@@ -981,25 +981,6 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
 	channel->index = index;
 	channel->mid_rid = -EINVAL;
 
-	/* Request the channel interrupt. */
-	scnprintf(pdev_irqname, sizeof(pdev_irqname), "ch%u", index);
-	irq = platform_get_irq_byname(pdev, pdev_irqname);
-	if (irq < 0)
-		return irq;
-
-	irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
-				 dev_name(dmac->dev), index);
-	if (!irqname)
-		return -ENOMEM;
-
-	ret = devm_request_threaded_irq(dmac->dev, irq, rz_dmac_irq_handler,
-					rz_dmac_irq_handler_thread, 0,
-					irqname, channel);
-	if (ret) {
-		dev_err(dmac->dev, "failed to request IRQ %u (%d)\n", irq, ret);
-		return ret;
-	}
-
 	/* Set io base address for each channel */
 	if (index < 8) {
 		channel->ch_base = dmac->base + CHANNEL_0_7_OFFSET +
@@ -1012,9 +993,9 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
 	}
 
 	/* Allocate descriptors */
-	lmdesc = dma_alloc_coherent(&pdev->dev,
-				    sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
-				    &channel->lmdesc.base_dma, GFP_KERNEL);
+	lmdesc = dmam_alloc_coherent(&pdev->dev,
+				     sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
+				     &channel->lmdesc.base_dma, GFP_KERNEL);
 	if (!lmdesc) {
 		dev_err(&pdev->dev, "Can't allocate memory (lmdesc)\n");
 		return -ENOMEM;
@@ -1030,7 +1011,24 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
 	INIT_LIST_HEAD(&channel->ld_free);
 	INIT_LIST_HEAD(&channel->ld_active);
 
-	return 0;
+	/* Request the channel interrupt. */
+	scnprintf(pdev_irqname, sizeof(pdev_irqname), "ch%u", index);
+	irq = platform_get_irq_byname(pdev, pdev_irqname);
+	if (irq < 0)
+		return irq;
+
+	irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
+				 dev_name(dmac->dev), index);
+	if (!irqname)
+		return -ENOMEM;
+
+	ret = devm_request_threaded_irq(dmac->dev, irq, rz_dmac_irq_handler,
+					rz_dmac_irq_handler_thread, 0,
+					irqname, channel);
+	if (ret)
+		dev_err(dmac->dev, "failed to request IRQ %u (%d)\n", irq, ret);
+
+	return ret;
 }
 
 static void rz_dmac_put_device(void *_dev)
@@ -1099,7 +1097,6 @@ static int rz_dmac_probe(struct platform_device *pdev)
 	const char *irqname = "error";
 	struct dma_device *engine;
 	struct rz_dmac *dmac;
-	int channel_num;
 	int ret;
 	int irq;
 	u8 i;
@@ -1132,18 +1129,6 @@ static int rz_dmac_probe(struct platform_device *pdev)
 			return PTR_ERR(dmac->ext_base);
 	}
 
-	/* Register interrupt handler for error */
-	irq = platform_get_irq_byname_optional(pdev, irqname);
-	if (irq > 0) {
-		ret = devm_request_irq(&pdev->dev, irq, rz_dmac_irq_handler, 0,
-				       irqname, NULL);
-		if (ret) {
-			dev_err(&pdev->dev, "failed to request IRQ %u (%d)\n",
-				irq, ret);
-			return ret;
-		}
-	}
-
 	/* Initialize the channels. */
 	INIT_LIST_HEAD(&dmac->engine.channels);
 
@@ -1169,6 +1154,18 @@ static int rz_dmac_probe(struct platform_device *pdev)
 			goto err;
 	}
 
+	/* Register interrupt handler for error */
+	irq = platform_get_irq_byname_optional(pdev, irqname);
+	if (irq > 0) {
+		ret = devm_request_irq(&pdev->dev, irq, rz_dmac_irq_handler, 0,
+				       irqname, NULL);
+		if (ret) {
+			dev_err(&pdev->dev, "failed to request IRQ %u (%d)\n",
+				irq, ret);
+			goto err;
+		}
+	}
+
 	/* Register the DMAC as a DMA provider for DT. */
 	ret = of_dma_controller_register(pdev->dev.of_node, rz_dmac_of_xlate,
 					 NULL);
@@ -1210,16 +1207,6 @@ static int rz_dmac_probe(struct platform_device *pdev)
 dma_register_err:
 	of_dma_controller_free(pdev->dev.of_node);
 err:
-	channel_num = i ? i - 1 : 0;
-	for (i = 0; i < channel_num; i++) {
-		struct rz_dmac_chan *channel = &dmac->channels[i];
-
-		dma_free_coherent(&pdev->dev,
-				  sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
-				  channel->lmdesc.base,
-				  channel->lmdesc.base_dma);
-	}
-
 	reset_control_assert(dmac->rstc);
 err_pm_runtime_put:
 	pm_runtime_put(&pdev->dev);
@@ -1232,18 +1219,9 @@ static int rz_dmac_probe(struct platform_device *pdev)
 static void rz_dmac_remove(struct platform_device *pdev)
 {
 	struct rz_dmac *dmac = platform_get_drvdata(pdev);
-	unsigned int i;
 
 	dma_async_device_unregister(&dmac->engine);
 	of_dma_controller_free(pdev->dev.of_node);
-	for (i = 0; i < dmac->n_channels; i++) {
-		struct rz_dmac_chan *channel = &dmac->channels[i];
-
-		dma_free_coherent(&pdev->dev,
-				  sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
-				  channel->lmdesc.base,
-				  channel->lmdesc.base_dma);
-	}
 	reset_control_assert(dmac->rstc);
 	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
-- 
2.43.0

[PATCH v5 02/17] dmaengine: sh: rz-dmac: Fix incorrect NULL check on list_first_entry()

[Claudiu Beznea]

The list passed as argument to list_first_entry() is expected to be not
empty. Use list_first_entry_or_null() to avoid dereferencing invalid
memory.

Fixes: 21323b118c16 ("dmaengine: sh: rz-dmac: Add device_tx_status() callback")
Cc: stable@vger.kernel.org
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
---

Changes in v5:
- none

Changes in v4:
- none, this patch is new

 drivers/dma/sh/rz-dmac.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
index 9f206a33dcc6..6d80cb668957 100644
--- a/drivers/dma/sh/rz-dmac.c
+++ b/drivers/dma/sh/rz-dmac.c
@@ -723,8 +723,8 @@ static u32 rz_dmac_chan_get_residue(struct rz_dmac_chan *channel,
 	u32 crla, crtb, i;
 
 	/* Get current processing virtual descriptor */
-	current_desc = list_first_entry(&channel->ld_active,
-					struct rz_dmac_desc, node);
+	current_desc = list_first_entry_or_null(&channel->ld_active,
+						struct rz_dmac_desc, node);
 	if (!current_desc)
 		return 0;
 
-- 
2.43.0

Re: [PATCH v5 01/17] dmaengine: sh: rz-dmac: Move interrupt request after everything is set up

[Frank Li]

On Tue, May 12, 2026 at 03:12:02PM +0300, Claudiu Beznea wrote:
> Once the interrupt is requested, the interrupt handler may run immediately.
> Since the IRQ handler can access channel->ch_base, which is initialized
> only after requesting the IRQ, this may lead to invalid memory access.
> Likewise, the IRQ thread may access uninitialized data (the ld_free,
> ld_queue, and ld_active lists), which may also lead to issues.
>
> Request the interrupts only after everything is set up. To keep the error
> path simpler, use dmam_alloc_coherent() instead of dma_alloc_coherent().
>
> Fixes: 5000d37042a6 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
> Cc: stable@vger.kernel.org
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

>
> Changes in v5:
> - none
>
> Changes in v4:
> - none, this patch is new
>
>  drivers/dma/sh/rz-dmac.c | 88 +++++++++++++++-------------------------
>  1 file changed, 33 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
> index 625ff29024de..9f206a33dcc6 100644
> --- a/drivers/dma/sh/rz-dmac.c
> +++ b/drivers/dma/sh/rz-dmac.c
> @@ -981,25 +981,6 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
>  	channel->index = index;
>  	channel->mid_rid = -EINVAL;
>
> -	/* Request the channel interrupt. */
> -	scnprintf(pdev_irqname, sizeof(pdev_irqname), "ch%u", index);
> -	irq = platform_get_irq_byname(pdev, pdev_irqname);
> -	if (irq < 0)
> -		return irq;
> -
> -	irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
> -				 dev_name(dmac->dev), index);
> -	if (!irqname)
> -		return -ENOMEM;
> -
> -	ret = devm_request_threaded_irq(dmac->dev, irq, rz_dmac_irq_handler,
> -					rz_dmac_irq_handler_thread, 0,
> -					irqname, channel);
> -	if (ret) {
> -		dev_err(dmac->dev, "failed to request IRQ %u (%d)\n", irq, ret);
> -		return ret;
> -	}
> -
>  	/* Set io base address for each channel */
>  	if (index < 8) {
>  		channel->ch_base = dmac->base + CHANNEL_0_7_OFFSET +
> @@ -1012,9 +993,9 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
>  	}
>
>  	/* Allocate descriptors */
> -	lmdesc = dma_alloc_coherent(&pdev->dev,
> -				    sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
> -				    &channel->lmdesc.base_dma, GFP_KERNEL);
> +	lmdesc = dmam_alloc_coherent(&pdev->dev,
> +				     sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
> +				     &channel->lmdesc.base_dma, GFP_KERNEL);
>  	if (!lmdesc) {
>  		dev_err(&pdev->dev, "Can't allocate memory (lmdesc)\n");
>  		return -ENOMEM;
> @@ -1030,7 +1011,24 @@ static int rz_dmac_chan_probe(struct rz_dmac *dmac,
>  	INIT_LIST_HEAD(&channel->ld_free);
>  	INIT_LIST_HEAD(&channel->ld_active);
>
> -	return 0;
> +	/* Request the channel interrupt. */
> +	scnprintf(pdev_irqname, sizeof(pdev_irqname), "ch%u", index);
> +	irq = platform_get_irq_byname(pdev, pdev_irqname);
> +	if (irq < 0)
> +		return irq;
> +
> +	irqname = devm_kasprintf(dmac->dev, GFP_KERNEL, "%s:%u",
> +				 dev_name(dmac->dev), index);
> +	if (!irqname)
> +		return -ENOMEM;
> +
> +	ret = devm_request_threaded_irq(dmac->dev, irq, rz_dmac_irq_handler,
> +					rz_dmac_irq_handler_thread, 0,
> +					irqname, channel);
> +	if (ret)
> +		dev_err(dmac->dev, "failed to request IRQ %u (%d)\n", irq, ret);
> +
> +	return ret;
>  }
>
>  static void rz_dmac_put_device(void *_dev)
> @@ -1099,7 +1097,6 @@ static int rz_dmac_probe(struct platform_device *pdev)
>  	const char *irqname = "error";
>  	struct dma_device *engine;
>  	struct rz_dmac *dmac;
> -	int channel_num;
>  	int ret;
>  	int irq;
>  	u8 i;
> @@ -1132,18 +1129,6 @@ static int rz_dmac_probe(struct platform_device *pdev)
>  			return PTR_ERR(dmac->ext_base);
>  	}
>
> -	/* Register interrupt handler for error */
> -	irq = platform_get_irq_byname_optional(pdev, irqname);
> -	if (irq > 0) {
> -		ret = devm_request_irq(&pdev->dev, irq, rz_dmac_irq_handler, 0,
> -				       irqname, NULL);
> -		if (ret) {
> -			dev_err(&pdev->dev, "failed to request IRQ %u (%d)\n",
> -				irq, ret);
> -			return ret;
> -		}
> -	}
> -
>  	/* Initialize the channels. */
>  	INIT_LIST_HEAD(&dmac->engine.channels);
>
> @@ -1169,6 +1154,18 @@ static int rz_dmac_probe(struct platform_device *pdev)
>  			goto err;
>  	}
>
> +	/* Register interrupt handler for error */
> +	irq = platform_get_irq_byname_optional(pdev, irqname);
> +	if (irq > 0) {
> +		ret = devm_request_irq(&pdev->dev, irq, rz_dmac_irq_handler, 0,
> +				       irqname, NULL);
> +		if (ret) {
> +			dev_err(&pdev->dev, "failed to request IRQ %u (%d)\n",
> +				irq, ret);
> +			goto err;
> +		}
> +	}
> +
>  	/* Register the DMAC as a DMA provider for DT. */
>  	ret = of_dma_controller_register(pdev->dev.of_node, rz_dmac_of_xlate,
>  					 NULL);
> @@ -1210,16 +1207,6 @@ static int rz_dmac_probe(struct platform_device *pdev)
>  dma_register_err:
>  	of_dma_controller_free(pdev->dev.of_node);
>  err:
> -	channel_num = i ? i - 1 : 0;
> -	for (i = 0; i < channel_num; i++) {
> -		struct rz_dmac_chan *channel = &dmac->channels[i];
> -
> -		dma_free_coherent(&pdev->dev,
> -				  sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
> -				  channel->lmdesc.base,
> -				  channel->lmdesc.base_dma);
> -	}
> -
>  	reset_control_assert(dmac->rstc);
>  err_pm_runtime_put:
>  	pm_runtime_put(&pdev->dev);
> @@ -1232,18 +1219,9 @@ static int rz_dmac_probe(struct platform_device *pdev)
>  static void rz_dmac_remove(struct platform_device *pdev)
>  {
>  	struct rz_dmac *dmac = platform_get_drvdata(pdev);
> -	unsigned int i;
>
>  	dma_async_device_unregister(&dmac->engine);
>  	of_dma_controller_free(pdev->dev.of_node);
> -	for (i = 0; i < dmac->n_channels; i++) {
> -		struct rz_dmac_chan *channel = &dmac->channels[i];
> -
> -		dma_free_coherent(&pdev->dev,
> -				  sizeof(struct rz_lmdesc) * DMAC_NR_LMDESC,
> -				  channel->lmdesc.base,
> -				  channel->lmdesc.base_dma);
> -	}
>  	reset_control_assert(dmac->rstc);
>  	pm_runtime_put(&pdev->dev);
>  	pm_runtime_disable(&pdev->dev);
> --
> 2.43.0
>

Re: [PATCH v5 02/17] dmaengine: sh: rz-dmac: Fix incorrect NULL check on list_first_entry()

[Frank Li]

On Tue, May 12, 2026 at 03:12:03PM +0300, Claudiu Beznea wrote:
> The list passed as argument to list_first_entry() is expected to be not
> empty.

Little confused,

#define list_first_entry_or_null(ptr, type, member) ({ \
	struct list_head *head__ = (ptr); \
	struct list_head *pos__ = READ_ONCE(head__->next); \
	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
})


both list passed to list_first_entry() or list_first_entry_or_null() must
be not NULL.

The return value is difference.

Fix incorrect NULL check for list_first_entry()

list_first_entry() does not return NULL when the list is empty,
making the existing NULL check invalid. Use list_first_entry_or_null()
instead.

Frank

> Use list_first_entry_or_null() to avoid dereferencing invalid
> memory.
>
> Fixes: 21323b118c16 ("dmaengine: sh: rz-dmac: Add device_tx_status() callback")
> Cc: stable@vger.kernel.org
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> ---

>
> Changes in v5:
> - none
>
> Changes in v4:
> - none, this patch is new
>
>  drivers/dma/sh/rz-dmac.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
> index 9f206a33dcc6..6d80cb668957 100644
> --- a/drivers/dma/sh/rz-dmac.c
> +++ b/drivers/dma/sh/rz-dmac.c
> @@ -723,8 +723,8 @@ static u32 rz_dmac_chan_get_residue(struct rz_dmac_chan *channel,
>  	u32 crla, crtb, i;
>
>  	/* Get current processing virtual descriptor */
> -	current_desc = list_first_entry(&channel->ld_active,
> -					struct rz_dmac_desc, node);
> +	current_desc = list_first_entry_or_null(&channel->ld_active,
> +						struct rz_dmac_desc, node);
>  	if (!current_desc)
>  		return 0;
>
> --
> 2.43.0
>

Re: [PATCH v5 02/17] dmaengine: sh: rz-dmac: Fix incorrect NULL check on list_first_entry()

[Claudiu Beznea]

Hi, Frank,

On 5/12/26 23:35, Frank Li wrote:
> On Tue, May 12, 2026 at 03:12:03PM +0300, Claudiu Beznea wrote:
>> The list passed as argument to list_first_entry() is expected to be not
>> empty.
> 
> Little confused,
> 
> #define list_first_entry_or_null(ptr, type, member) ({ \
> 	struct list_head *head__ = (ptr); \
> 	struct list_head *pos__ = READ_ONCE(head__->next); \
> 	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
> })
> 
> 
> both list passed to list_first_entry() or list_first_entry_or_null() must
> be not NULL.

The intention was to to express that checking the pointer returned by 
list_first_entry() may lead to problems. I'll adjust the description to be more 
clear.

-- 
Thank you,
Claudiu