[PATCH] board-dm644x-evm: fix 2 missing-check bugs in evm_led_setup()

[PATCH] board-dm644x-evm: fix 2 missing-check bugs in evm_led_setup()

[Gen Zhang]

In evm_led_setup(), the allocation result of platform_device_alloc() and 
platform_device_add_data() should be checked.

Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
---
diff --git a/arch/arm/mach-davinci/board-dm644x-evm.c b/arch/arm/mach-davinci/board-dm644x-evm.c
index 9d87d4e..9cd2785 100644
--- a/arch/arm/mach-davinci/board-dm644x-evm.c
+++ b/arch/arm/mach-davinci/board-dm644x-evm.c
@@ -352,15 +352,20 @@ evm_led_setup(struct i2c_client *client, int gpio, unsigned ngpio, void *c)
 	 * device unregistration ...
 	 */
 	evm_led_dev = platform_device_alloc("leds-gpio", 0);
-	platform_device_add_data(evm_led_dev,
+	if (!evm_led_dev)
+		return -ENOMEM;
+	status = platform_device_add_data(evm_led_dev,
 			&evm_led_data, sizeof evm_led_data);
+	if (status)
+		goto err;
 
 	evm_led_dev->dev.parent = &client->dev;
 	status = platform_device_add(evm_led_dev);
-	if (status < 0) {
-		platform_device_put(evm_led_dev);
-		evm_led_dev = NULL;
-	}
+	if (status)
+		goto err;
+err:
+	platform_device_put(evm_led_dev);
+	evm_led_dev = NULL;
 	return status;
 }
 

Re: [PATCH] board-dm644x-evm: fix 2 missing-check bugs in evm_led_setup()

[Russell King - ARM Linux admin]

On Fri, Dec 27, 2019 at 10:39:21AM +0800, Gen Zhang wrote:
> In evm_led_setup(), the allocation result of platform_device_alloc() and 
> platform_device_add_data() should be checked.
> 
> Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> ---
> diff --git a/arch/arm/mach-davinci/board-dm644x-evm.c b/arch/arm/mach-davinci/board-dm644x-evm.c
> index 9d87d4e..9cd2785 100644
> --- a/arch/arm/mach-davinci/board-dm644x-evm.c
> +++ b/arch/arm/mach-davinci/board-dm644x-evm.c
> @@ -352,15 +352,20 @@ evm_led_setup(struct i2c_client *client, int gpio, unsigned ngpio, void *c)
>  	 * device unregistration ...
>  	 */
>  	evm_led_dev = platform_device_alloc("leds-gpio", 0);
> -	platform_device_add_data(evm_led_dev,
> +	if (!evm_led_dev)
> +		return -ENOMEM;
> +	status = platform_device_add_data(evm_led_dev,
>  			&evm_led_data, sizeof evm_led_data);
> +	if (status)
> +		goto err;
>  
>  	evm_led_dev->dev.parent = &client->dev;
>  	status = platform_device_add(evm_led_dev);
> -	if (status < 0) {
> -		platform_device_put(evm_led_dev);
> -		evm_led_dev = NULL;
> -	}
> +	if (status)
> +		goto err;
> +err:
> +	platform_device_put(evm_led_dev);
> +	evm_led_dev = NULL;

Please look again at the above change very closely. You will want to
send an updated patch.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
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Re: [PATCH] board-dm644x-evm: fix 2 missing-check bugs in evm_led_setup()

[Gen Zhang]

On Fri, Dec 27, 2019 at 04:01:42PM +0000, Russell King - ARM Linux admin wrote:
> On Fri, Dec 27, 2019 at 10:39:21AM +0800, Gen Zhang wrote:
> > In evm_led_setup(), the allocation result of platform_device_alloc() and 
> > platform_device_add_data() should be checked.
> > 
> > Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> > ---
> > diff --git a/arch/arm/mach-davinci/board-dm644x-evm.c b/arch/arm/mach-davinci/board-dm644x-evm.c
> > index 9d87d4e..9cd2785 100644
> > --- a/arch/arm/mach-davinci/board-dm644x-evm.c
> > +++ b/arch/arm/mach-davinci/board-dm644x-evm.c
> > @@ -352,15 +352,20 @@ evm_led_setup(struct i2c_client *client, int gpio, unsigned ngpio, void *c)
> >  	 * device unregistration ...
> >  	 */
> >  	evm_led_dev = platform_device_alloc("leds-gpio", 0);
> > -	platform_device_add_data(evm_led_dev,
> > +	if (!evm_led_dev)
> > +		return -ENOMEM;
> > +	status = platform_device_add_data(evm_led_dev,
> >  			&evm_led_data, sizeof evm_led_data);
> > +	if (status)
> > +		goto err;
> >  
> >  	evm_led_dev->dev.parent = &client->dev;
> >  	status = platform_device_add(evm_led_dev);
> > -	if (status < 0) {
> > -		platform_device_put(evm_led_dev);
> > -		evm_led_dev = NULL;
> > -	}
> > +	if (status)
> > +		goto err;
> > +err:
> > +	platform_device_put(evm_led_dev);
> > +	evm_led_dev = NULL;
> 
> Please look again at the above change very closely. You will want to
> send an updated patch.
> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> According to speedtest.net: 11.9Mbps down 500kbps up

Thanks for your reply. You mean the if (state < 0 ) to if (state) or
anything else? Please point out directly.

Best,
Gen

Re: [PATCH] board-dm644x-evm: fix 2 missing-check bugs in evm_led_setup()

[Russell King - ARM Linux admin]

On Sat, Dec 28, 2019 at 09:19:30PM +0800, Gen Zhang wrote:
> On Fri, Dec 27, 2019 at 04:01:42PM +0000, Russell King - ARM Linux admin wrote:
> > On Fri, Dec 27, 2019 at 10:39:21AM +0800, Gen Zhang wrote:
> > > In evm_led_setup(), the allocation result of platform_device_alloc() and 
> > > platform_device_add_data() should be checked.
> > > 
> > > Signed-off-by: Gen Zhang <blackgod016574@gmail.com>
> > > ---
> > > diff --git a/arch/arm/mach-davinci/board-dm644x-evm.c b/arch/arm/mach-davinci/board-dm644x-evm.c
> > > index 9d87d4e..9cd2785 100644
> > > --- a/arch/arm/mach-davinci/board-dm644x-evm.c
> > > +++ b/arch/arm/mach-davinci/board-dm644x-evm.c
> > > @@ -352,15 +352,20 @@ evm_led_setup(struct i2c_client *client, int gpio, unsigned ngpio, void *c)
> > >  	 * device unregistration ...
> > >  	 */
> > >  	evm_led_dev = platform_device_alloc("leds-gpio", 0);
> > > -	platform_device_add_data(evm_led_dev,
> > > +	if (!evm_led_dev)
> > > +		return -ENOMEM;
> > > +	status = platform_device_add_data(evm_led_dev,
> > >  			&evm_led_data, sizeof evm_led_data);
> > > +	if (status)
> > > +		goto err;
> > >  
> > >  	evm_led_dev->dev.parent = &client->dev;
> > >  	status = platform_device_add(evm_led_dev);
> > > -	if (status < 0) {
> > > -		platform_device_put(evm_led_dev);
> > > -		evm_led_dev = NULL;
> > > -	}
> > > +	if (status)
> > > +		goto err;
> > > +err:
> > > +	platform_device_put(evm_led_dev);
> > > +	evm_led_dev = NULL;
> > 
> > Please look again at the above change very closely. You will want to
> > send an updated patch.
> > 
> > -- 
> > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> > FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> > According to speedtest.net: 11.9Mbps down 500kbps up
> 
> Thanks for your reply. You mean the if (state < 0 ) to if (state) or
> anything else? Please point out directly.

This is the old everything-successful path through the code:

	platform_device_alloc()
	platform_device_add_data()
	platform_device_add()
	evm_led_dev is set to the device

This is the new everything-successful path through the code:

	platform_device_alloc()
	platform_device_add_data()
	platform_device_add()
	platform_device_put()
	evm_led_dev = NULL

And, specifically, the code sequence (I quote from your patch):

	if (status)
		goto err;
err:

is very stupid; it might as well not exist at all.

Since other code references evm_led_dev, one can assume that we do
not want it to be NULL for the success path. So, taking all this
together, your patch is very very wrong, and I also find it very
worrying too.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up

Re: [PATCH] board-dm644x-evm: fix 2 missing-check bugs in evm_led_setup()

[Gen Zhang]

On Sat, Dec 28, 2019 at 01:48:24PM +0000, Russell King - ARM Linux admin wrote:
 
> This is the old everything-successful path through the code:
> 
> 	platform_device_alloc()
> 	platform_device_add_data()
> 	platform_device_add()
> 	evm_led_dev is set to the device
> 
> This is the new everything-successful path through the code:
> 
> 	platform_device_alloc()
> 	platform_device_add_data()
> 	platform_device_add()
> 	platform_device_put()
> 	evm_led_dev = NULL
Thanks for your reply. Adding a return may handle this.
	successful path:
	platform_device_alloc()
 	platform_device_add_data()
 	platform_device_add()
	return status
 	
	error path:
	platform_device_put()
 	evm_led_dev = NULL
	return status
correct?

> 
> And, specifically, the code sequence (I quote from your patch):
> 
> 	if (status)
> 		goto err;
> err:
> 
> is very stupid; it might as well not exist at all.

Well, you have to admit that the result of platform_device_alloc(),
platform_device_add_data() and platform_device_add() should be checked,
and error should be handled.

e.g., there are 124 call sites of platform_device_add_data() in Linux. Only 24
are not checked, and most of them are in arm subsystem.

Look forward to deeper discussion of this problem.

Best,
Gen
> 
> Since other code references evm_led_dev, one can assume that we do
> not want it to be NULL for the success path. So, taking all this
> together, your patch is very very wrong, and I also find it very
> worrying too.
> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> According to speedtest.net: 11.9Mbps down 500kbps up