[PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

[PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

[Hyeonggon Yoo]

line6_init_cap_control doesn't free resources properly when allocations
like kmalloc, usb_alloc_urb fails. It can cause memory leak when some
allocations succeed, and then an error occurs.

This patch makes line6_init_cap_control to properly free the resources,
freeing previously allocated resources when there's an error.

Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
 sound/usb/line6/driver.c | 36 +++++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 9602929b7de9..6991cb855023 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -688,34 +688,52 @@ static int line6_init_cap_control(struct usb_line6 *line6)
 
 	/* initialize USB buffers: */
 	line6->buffer_listen = kmalloc(LINE6_BUFSIZE_LISTEN, GFP_KERNEL);
-	if (!line6->buffer_listen)
-		return -ENOMEM;
+	if (!line6->buffer_listen) {
+		ret = -ENOMEM;
+		goto fail_ret;
+	}
 
 	line6->urb_listen = usb_alloc_urb(0, GFP_KERNEL);
-	if (!line6->urb_listen)
-		return -ENOMEM;
+	if (!line6->urb_listen) {
+		ret = -ENOMEM;
+		goto fail1;
+	}
 
 	if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {
 		line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
-		if (!line6->buffer_message)
-			return -ENOMEM;
+		if (!line6->buffer_message) {
+			ret = -ENOMEM;
+			goto fail2;
+		}
 
 		ret = line6_init_midi(line6);
 		if (ret < 0)
-			return ret;
+			goto fail3;
 	} else {
 		ret = line6_hwdep_init(line6);
 		if (ret < 0)
-			return ret;
+			goto fail2;
 	}
 
 	ret = line6_start_listen(line6);
 	if (ret < 0) {
 		dev_err(line6->ifcdev, "cannot start listening: %d\n", ret);
-		return ret;
+		if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI)
+			goto fail3;
+		else
+			goto fail2;
 	}
 
 	return 0;
+
+fail3:
+	kfree(line6->buffer_message);
+fail2:
+	usb_free_urb(line6->urb_listen);
+fail1:
+	kfree(line6->buffer_listen);
+fail_ret:
+	return ret;
 }
 
 static void line6_startup_work(struct work_struct *work)
-- 
2.25.1

Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

[Hyeonggon Yoo]

added an error handling code. It builds well,
but I don't have the device. So please review it (and test if you have one)

if you think I can improve something, please tell me.
I'll send v2.

Thanks,
Hyeonggon

Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

[Takashi Iwai]

On Mon, 24 May 2021 19:36:44 +0200,
Hyeonggon Yoo wrote:
> 
> line6_init_cap_control doesn't free resources properly when allocations
> like kmalloc, usb_alloc_urb fails. It can cause memory leak when some
> allocations succeed, and then an error occurs.
> 
> This patch makes line6_init_cap_control to properly free the resources,
> freeing previously allocated resources when there's an error.
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> ---
>  sound/usb/line6/driver.c | 36 +++++++++++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> index 9602929b7de9..6991cb855023 100644
> --- a/sound/usb/line6/driver.c
> +++ b/sound/usb/line6/driver.c
> @@ -688,34 +688,52 @@ static int line6_init_cap_control(struct usb_line6 *line6)
>  
>  	/* initialize USB buffers: */
>  	line6->buffer_listen = kmalloc(LINE6_BUFSIZE_LISTEN, GFP_KERNEL);
> -	if (!line6->buffer_listen)
> -		return -ENOMEM;
> +	if (!line6->buffer_listen) {
> +		ret = -ENOMEM;
> +		goto fail_ret;
> +	}
>  
>  	line6->urb_listen = usb_alloc_urb(0, GFP_KERNEL);
> -	if (!line6->urb_listen)
> -		return -ENOMEM;
> +	if (!line6->urb_listen) {
> +		ret = -ENOMEM;
> +		goto fail1;
> +	}
>  
>  	if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {
>  		line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
> -		if (!line6->buffer_message)
> -			return -ENOMEM;
> +		if (!line6->buffer_message) {
> +			ret = -ENOMEM;
> +			goto fail2;
> +		}
>  
>  		ret = line6_init_midi(line6);
>  		if (ret < 0)
> -			return ret;
> +			goto fail3;
>  	} else {
>  		ret = line6_hwdep_init(line6);
>  		if (ret < 0)
> -			return ret;
> +			goto fail2;
>  	}
>  
>  	ret = line6_start_listen(line6);
>  	if (ret < 0) {
>  		dev_err(line6->ifcdev, "cannot start listening: %d\n", ret);
> -		return ret;
> +		if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI)
> +			goto fail3;
> +		else
> +			goto fail2;
>  	}
>  
>  	return 0;
> +
> +fail3:
> +	kfree(line6->buffer_message);
> +fail2:
> +	usb_free_urb(line6->urb_listen);
> +fail1:
> +	kfree(line6->buffer_listen);
> +fail_ret:
> +	return ret;
>  }

Those resources are freed in the common destructor of the card
instance, line6_destruct(), at disconnect callback, so it's redundant
to release them here; even worse, since you haven't re-initialize with
NULL, this change would lead to double-free.


thanks,

Takashi

Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

[Takashi Iwai]

On Mon, 24 May 2021 19:36:44 +0200,
Hyeonggon Yoo wrote:
> 
> line6_init_cap_control doesn't free resources properly when allocations
> like kmalloc, usb_alloc_urb fails. It can cause memory leak when some
> allocations succeed, and then an error occurs.
> 
> This patch makes line6_init_cap_control to properly free the resources,
> freeing previously allocated resources when there's an error.
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> ---
>  sound/usb/line6/driver.c | 36 +++++++++++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
> index 9602929b7de9..6991cb855023 100644
> --- a/sound/usb/line6/driver.c
> +++ b/sound/usb/line6/driver.c
> @@ -688,34 +688,52 @@ static int line6_init_cap_control(struct usb_line6 *line6)
>  
>  	/* initialize USB buffers: */
>  	line6->buffer_listen = kmalloc(LINE6_BUFSIZE_LISTEN, GFP_KERNEL);
> -	if (!line6->buffer_listen)
> -		return -ENOMEM;
> +	if (!line6->buffer_listen) {
> +		ret = -ENOMEM;
> +		goto fail_ret;
> +	}
>  
>  	line6->urb_listen = usb_alloc_urb(0, GFP_KERNEL);
> -	if (!line6->urb_listen)
> -		return -ENOMEM;
> +	if (!line6->urb_listen) {
> +		ret = -ENOMEM;
> +		goto fail1;
> +	}
>  
>  	if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {
>  		line6->buffer_message = kmalloc(LINE6_MIDI_MESSAGE_MAXLEN, GFP_KERNEL);
> -		if (!line6->buffer_message)
> -			return -ENOMEM;
> +		if (!line6->buffer_message) {
> +			ret = -ENOMEM;
> +			goto fail2;
> +		}
>  
>  		ret = line6_init_midi(line6);
>  		if (ret < 0)
> -			return ret;
> +			goto fail3;
>  	} else {
>  		ret = line6_hwdep_init(line6);
>  		if (ret < 0)
> -			return ret;
> +			goto fail2;
>  	}
>  
>  	ret = line6_start_listen(line6);
>  	if (ret < 0) {
>  		dev_err(line6->ifcdev, "cannot start listening: %d\n", ret);
> -		return ret;
> +		if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI)
> +			goto fail3;
> +		else
> +			goto fail2;
>  	}
>  
>  	return 0;
> +
> +fail3:
> +	kfree(line6->buffer_message);
> +fail2:
> +	usb_free_urb(line6->urb_listen);
> +fail1:
> +	kfree(line6->buffer_listen);
> +fail_ret:
> +	return ret;
>  }

Those resources are freed in the common destructor of the card
instance, line6_destruct(), at disconnect callback, so it's redundant
to release them here; even worse, since you haven't re-initialize with
NULL, this change would lead to double-free.


thanks,

Takashi

Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

[Hyeonggon Yoo]

On Tue, May 25, 2021 at 09:05:13AM +0200, Takashi Iwai wrote:
> Those resources are freed in the common destructor of the card
> instance, line6_destruct(),

Oh my god, I missed line6_destruct.

> at disconnect callback, so it's redundant
> to release them here; even worse, since you haven't re-initialize with
> NULL, this change would lead to double-free.

Yes then it can cause double-free..

>
>
> thanks,
>
> Takashi

I made a mistake, I'm so sorry to take your time...

Thanks,
Hyeonggon

Re: [PATCH] ALSA: line6: Improve poor error handling in line6_init_cap_control

[Hyeonggon Yoo]

On Tue, May 25, 2021 at 09:05:13AM +0200, Takashi Iwai wrote:
> Those resources are freed in the common destructor of the card
> instance, line6_destruct(),

Oh my god, I missed line6_destruct.

> at disconnect callback, so it's redundant
> to release them here; even worse, since you haven't re-initialize with
> NULL, this change would lead to double-free.

Yes then it can cause double-free..

>
>
> thanks,
>
> Takashi

I made a mistake, I'm so sorry to take your time...

Thanks,
Hyeonggon