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

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Message-ID: <20190917063004.GG18977@kadam>
Date:   Tue, 17 Sep 2019 09:33:47 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Navid Emamdoost <navid.emamdoost@...il.com>
Cc:     devel@...verdev.osuosl.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>, kjlu@....edu,
        linux-kernel@...r.kernel.org, Ian Abbott <abbotti@....co.uk>,
        emamd001@....edu, smccaman@....edu
Subject: Re: [PATCH] staging: comedi: drivers: prevent memory leak

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. */

regards,
dan carpenter