linux-kernel - Re: [PATCH] staging: comedi: drivers: prevent memory leak

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Date:   Tue, 17 Sep 2019 11:13:15 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Navid Emamdoost <navid.emamdoost@...il.com>
Cc:     devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>, kjlu@....edu,
        linux-kernel@...r.kernel.org, emamd001@....edu, smccaman@....edu
Subject: Re: [PATCH] staging: comedi: drivers: prevent memory leak

On 17/09/2019 07:33, Dan Carpenter wrote:
> On Mon, Sep 16, 2019 at 09:41:43PM -0500, Navid Emamdoost wrote:
>> In das1800_attach, the buffer allocated via kmalloc_array needs to be
>> released if an error happens.
>>
>> Signed-off-by: Navid Emamdoost <navid.emamdoost@...il.com>
> 
> Commedit calls ->detach() if the ->attach() fails so this patch would
> lead to a double free.  See comedi_device_attach():
> 
> drivers/staging/comedi/drivers.c
>     983          }
>     984          if (!driv->attach) {
>     985                  /* driver does not support manual configuration */
>     986                  dev_warn(dev->class_dev,
>     987                           "driver '%s' does not support attach using comedi_config\n",
>     988                           driv->driver_name);
>     989                  module_put(driv->module);
>     990                  ret = -EIO;
>     991                  goto out;
>     992          }
>     993          dev->driver = driv;
>     994          dev->board_name = dev->board_ptr ? *(const char **)dev->board_ptr
>     995                                           : dev->driver->driver_name;
>     996          ret = driv->attach(dev, it);
>                        ^^^^^^^^^^^^^^^^^^^^^
>     997          if (ret >= 0)
>     998                  ret = comedi_device_postconfig(dev);
>     999          if (ret < 0) {
>    1000                  comedi_device_detach(dev);
>                          ^^^^^^^^^^^^^^^^^^^^^^^^^
> 
>    1001                  module_put(driv->module);
>    1002          }
>    1003          /* On success, the driver module count has been incremented. */

Yes, everything should be freed properly by comedi_device_detach(). 
 From comedi_device_detach(), some of the stuff is freed by 
dev->driver->detach(), and the remainder is freed by 
comedi_device_detach_cleanup().

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