tty: owl-uart: fix call balance of owl_port->clk handling routines

[PATCH] tty: owl-uart: fix call balance of owl_port->clk handling routines

Posted by Vitalii Mordan 10 months, 1 week ago

If owl_port->clk was enabled in owl_uart_probe(), it must be disabled in
all error paths to ensure proper cleanup. However, if uart_add_one_port()
returns an error in owl_uart_probe(), the owl_port->clk clock will not be
disabled.

Use the devm_clk_get_enabled() helper function to ensure proper call
balance for owl_port->clk.

Found by Linux Verification Center (linuxtesting.org) with Klever.

Fixes: abf42d2f333b ("tty: serial: owl: add "much needed" clk_prepare_enable()")
Cc: stable@vger.kernel.org
Signed-off-by: Vitalii Mordan <mordan@ispras.ru>
---
 drivers/tty/serial/owl-uart.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
index 0542882cfbbe..64446820437c 100644
--- a/drivers/tty/serial/owl-uart.c
+++ b/drivers/tty/serial/owl-uart.c
@@ -680,18 +680,12 @@ static int owl_uart_probe(struct platform_device *pdev)
 	if (!owl_port)
 		return -ENOMEM;
 
-	owl_port->clk = devm_clk_get(&pdev->dev, NULL);
+	owl_port->clk = devm_clk_get_enabled(&pdev->dev, NULL);
 	if (IS_ERR(owl_port->clk)) {
-		dev_err(&pdev->dev, "could not get clk\n");
+		dev_err(&pdev->dev, "could not get and enable clk\n");
 		return PTR_ERR(owl_port->clk);
 	}
 
-	ret = clk_prepare_enable(owl_port->clk);
-	if (ret) {
-		dev_err(&pdev->dev, "could not enable clk\n");
-		return ret;
-	}
-
 	owl_port->port.dev = &pdev->dev;
 	owl_port->port.line = pdev->id;
 	owl_port->port.type = PORT_OWL;
@@ -701,7 +695,6 @@ static int owl_uart_probe(struct platform_device *pdev)
 	owl_port->port.uartclk = clk_get_rate(owl_port->clk);
 	if (owl_port->port.uartclk == 0) {
 		dev_err(&pdev->dev, "clock rate is zero\n");
-		clk_disable_unprepare(owl_port->clk);
 		return -EINVAL;
 	}
 	owl_port->port.flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP | UPF_LOW_LATENCY;
@@ -725,7 +718,6 @@ static void owl_uart_remove(struct platform_device *pdev)
 
 	uart_remove_one_port(&owl_uart_driver, &owl_port->port);
 	owl_uart_ports[pdev->id] = NULL;
-	clk_disable_unprepare(owl_port->clk);
 }
 
 static struct platform_driver owl_uart_platform_driver = {
-- 
2.25.1

Re: [PATCH] tty: owl-uart: fix call balance of owl_port->clk handling routines

Posted by Manivannan Sadhasivam 10 months ago

On Thu, Feb 13, 2025 at 02:24:16PM +0300, Vitalii Mordan wrote:
> If owl_port->clk was enabled in owl_uart_probe(), it must be disabled in
> all error paths to ensure proper cleanup. However, if uart_add_one_port()
> returns an error in owl_uart_probe(), the owl_port->clk clock will not be
> disabled.
> 
> Use the devm_clk_get_enabled() helper function to ensure proper call
> balance for owl_port->clk.
> 
> Found by Linux Verification Center (linuxtesting.org) with Klever.
> 
> Fixes: abf42d2f333b ("tty: serial: owl: add "much needed" clk_prepare_enable()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Vitalii Mordan <mordan@ispras.ru>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

- Mani

> ---
>  drivers/tty/serial/owl-uart.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
> index 0542882cfbbe..64446820437c 100644
> --- a/drivers/tty/serial/owl-uart.c
> +++ b/drivers/tty/serial/owl-uart.c
> @@ -680,18 +680,12 @@ static int owl_uart_probe(struct platform_device *pdev)
>  	if (!owl_port)
>  		return -ENOMEM;
>  
> -	owl_port->clk = devm_clk_get(&pdev->dev, NULL);
> +	owl_port->clk = devm_clk_get_enabled(&pdev->dev, NULL);
>  	if (IS_ERR(owl_port->clk)) {
> -		dev_err(&pdev->dev, "could not get clk\n");
> +		dev_err(&pdev->dev, "could not get and enable clk\n");
>  		return PTR_ERR(owl_port->clk);
>  	}
>  
> -	ret = clk_prepare_enable(owl_port->clk);
> -	if (ret) {
> -		dev_err(&pdev->dev, "could not enable clk\n");
> -		return ret;
> -	}
> -
>  	owl_port->port.dev = &pdev->dev;
>  	owl_port->port.line = pdev->id;
>  	owl_port->port.type = PORT_OWL;
> @@ -701,7 +695,6 @@ static int owl_uart_probe(struct platform_device *pdev)
>  	owl_port->port.uartclk = clk_get_rate(owl_port->clk);
>  	if (owl_port->port.uartclk == 0) {
>  		dev_err(&pdev->dev, "clock rate is zero\n");
> -		clk_disable_unprepare(owl_port->clk);
>  		return -EINVAL;
>  	}
>  	owl_port->port.flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP | UPF_LOW_LATENCY;
> @@ -725,7 +718,6 @@ static void owl_uart_remove(struct platform_device *pdev)
>  
>  	uart_remove_one_port(&owl_uart_driver, &owl_port->port);
>  	owl_uart_ports[pdev->id] = NULL;
> -	clk_disable_unprepare(owl_port->clk);
>  }
>  
>  static struct platform_driver owl_uart_platform_driver = {
> -- 
> 2.25.1
> 

-- 
மணிவண்ணன் சதாசிவம்

Re: [PATCH] tty: owl-uart: fix call balance of owl_port->clk handling routines

Posted by Manivannan Sadhasivam 10 months, 1 week ago

On Thu, Feb 13, 2025 at 02:24:16PM +0300, Vitalii Mordan wrote:
> If owl_port->clk was enabled in owl_uart_probe(), it must be disabled in
> all error paths to ensure proper cleanup. However, if uart_add_one_port()
> returns an error in owl_uart_probe(), the owl_port->clk clock will not be
> disabled.
> 
> Use the devm_clk_get_enabled() helper function to ensure proper call
> balance for owl_port->clk.
> 

Do not use newly introduced APIs to fix old bugs. The bug should be fixed
separately to allow backporting and the conversion should be done on top.

- Mani

> Found by Linux Verification Center (linuxtesting.org) with Klever.
> 
> Fixes: abf42d2f333b ("tty: serial: owl: add "much needed" clk_prepare_enable()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Vitalii Mordan <mordan@ispras.ru>
> ---
>  drivers/tty/serial/owl-uart.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
> index 0542882cfbbe..64446820437c 100644
> --- a/drivers/tty/serial/owl-uart.c
> +++ b/drivers/tty/serial/owl-uart.c
> @@ -680,18 +680,12 @@ static int owl_uart_probe(struct platform_device *pdev)
>  	if (!owl_port)
>  		return -ENOMEM;
>  
> -	owl_port->clk = devm_clk_get(&pdev->dev, NULL);
> +	owl_port->clk = devm_clk_get_enabled(&pdev->dev, NULL);
>  	if (IS_ERR(owl_port->clk)) {
> -		dev_err(&pdev->dev, "could not get clk\n");
> +		dev_err(&pdev->dev, "could not get and enable clk\n");
>  		return PTR_ERR(owl_port->clk);
>  	}
>  
> -	ret = clk_prepare_enable(owl_port->clk);
> -	if (ret) {
> -		dev_err(&pdev->dev, "could not enable clk\n");
> -		return ret;
> -	}
> -
>  	owl_port->port.dev = &pdev->dev;
>  	owl_port->port.line = pdev->id;
>  	owl_port->port.type = PORT_OWL;
> @@ -701,7 +695,6 @@ static int owl_uart_probe(struct platform_device *pdev)
>  	owl_port->port.uartclk = clk_get_rate(owl_port->clk);
>  	if (owl_port->port.uartclk == 0) {
>  		dev_err(&pdev->dev, "clock rate is zero\n");
> -		clk_disable_unprepare(owl_port->clk);
>  		return -EINVAL;
>  	}
>  	owl_port->port.flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP | UPF_LOW_LATENCY;
> @@ -725,7 +718,6 @@ static void owl_uart_remove(struct platform_device *pdev)
>  
>  	uart_remove_one_port(&owl_uart_driver, &owl_port->port);
>  	owl_uart_ports[pdev->id] = NULL;
> -	clk_disable_unprepare(owl_port->clk);
>  }
>  
>  static struct platform_driver owl_uart_platform_driver = {
> -- 
> 2.25.1
> 

-- 
மணிவண்ணன் சதாசிவம்

Re: [PATCH] tty: owl-uart: fix call balance of owl_port->clk handling routines

Posted by Fedor Pchelkin 10 months, 1 week ago

On Fri, 14. Feb 22:44, Manivannan Sadhasivam wrote:
> On Thu, Feb 13, 2025 at 02:24:16PM +0300, Vitalii Mordan wrote:
> > If owl_port->clk was enabled in owl_uart_probe(), it must be disabled in
> > all error paths to ensure proper cleanup. However, if uart_add_one_port()
> > returns an error in owl_uart_probe(), the owl_port->clk clock will not be
> > disabled.
> > 
> > Use the devm_clk_get_enabled() helper function to ensure proper call
> > balance for owl_port->clk.
> > 
> 
> Do not use newly introduced APIs to fix old bugs. The bug should be fixed
> separately to allow backporting and the conversion should be done on top.

These relatively new helpers are already available in all currently
supported stable kernels including 5.4.y.

Commit 7ef9651e9792 ("clk: Provide new devm_clk helpers for prepared and
enabled clocks") was conveniently backported there as a dependency for
the similar bug fixes.

Re: [PATCH] tty: owl-uart: fix call balance of owl_port->clk handling routines

Posted by Manivannan Sadhasivam 10 months ago

On Fri, Feb 14, 2025 at 09:39:09PM +0300, Fedor Pchelkin wrote:
> On Fri, 14. Feb 22:44, Manivannan Sadhasivam wrote:
> > On Thu, Feb 13, 2025 at 02:24:16PM +0300, Vitalii Mordan wrote:
> > > If owl_port->clk was enabled in owl_uart_probe(), it must be disabled in
> > > all error paths to ensure proper cleanup. However, if uart_add_one_port()
> > > returns an error in owl_uart_probe(), the owl_port->clk clock will not be
> > > disabled.
> > > 
> > > Use the devm_clk_get_enabled() helper function to ensure proper call
> > > balance for owl_port->clk.
> > > 
> > 
> > Do not use newly introduced APIs to fix old bugs. The bug should be fixed
> > separately to allow backporting and the conversion should be done on top.
> 
> These relatively new helpers are already available in all currently
> supported stable kernels including 5.4.y.
> 
> Commit 7ef9651e9792 ("clk: Provide new devm_clk helpers for prepared and
> enabled clocks") was conveniently backported there as a dependency for
> the similar bug fixes.

Ah, then fine with me.

- Mani

-- 
மணிவண்ணன் சதாசிவம்