linux-kernel - Re: [PATCH] media: em28xx: Fix possible memory leak of em28xx struct

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Date:   Mon, 3 May 2021 16:06:10 -0400
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Igor Matheus Andrade Torrente <igormtorrente@...il.com>,
        mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        hverkuil-cisco@...all.nl, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] media: em28xx: Fix possible memory leak of em28xx struct

Hi Igor,

On 5/3/21 11:37 AM, Igor Matheus Andrade Torrente wrote:
> The em28xx struct kref isn't being decreased after an error in the
> em28xx_ir_init, leading to a possible memory leak.
> 
> A kref_put is added to the error handler code.
> 
> Signed-off-by: Igor Matheus Andrade Torrente <igormtorrente@...il.com>
> ---
>   drivers/media/usb/em28xx/em28xx-input.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/em28xx/em28xx-input.c b/drivers/media/usb/em28xx/em28xx-input.c
> index 5aa15a7a49de..b89527014cad 100644
> --- a/drivers/media/usb/em28xx/em28xx-input.c
> +++ b/drivers/media/usb/em28xx/em28xx-input.c
> @@ -720,7 +720,8 @@ static int em28xx_ir_init(struct em28xx *dev)
>   			dev->board.has_ir_i2c = 0;
>   			dev_warn(&dev->intf->dev,
>   				 "No i2c IR remote control device found.\n");
> -			return -ENODEV;
> +			err = -ENODEV;
> +			goto ref_put;

This doesn't look right. em28xx_init_buttons() is already happened and
em28xx_shutdown_buttons() needs to be done from fini. fini needs to run
with this ref. If ref is released here, device might be released before
em28xx_shutdown_buttons() can run leading to potential use-after-free

>   		}
>   	}
>   
> @@ -735,7 +736,7 @@ static int em28xx_ir_init(struct em28xx *dev)
>   
>   	ir = kzalloc(sizeof(*ir), GFP_KERNEL);
>   	if (!ir)
> -		return -ENOMEM;
> +		goto ref_put;

This doesn't look right. Same comment as above. fini accounts for null
ir.

        em28xx_shutdown_buttons(dev);

         /* skip detach on non attached boards */
         if (!ir)
                 goto ref_put;


>   	rc = rc_allocate_device(RC_DRIVER_SCANCODE);
>   	if (!rc)
>   		goto error;
> @@ -839,6 +840,8 @@ static int em28xx_ir_init(struct em28xx *dev)
>   	dev->ir = NULL;
>   	rc_free_device(rc);
>   	kfree(ir);
> +ref_put:
> +	kref_put(&dev->ref, em28xx_free_device);
>   	return err;
>   }
>   
> 

thanks,
-- Shuah