gdrom: fix a memory leak bug

mainline inclusion
from mainline-5.0-rc1
commit 093c48213ee37c3c3ff1cf5ac1aa2a9d8bc66017
category: bugfix
bugzilla: 6749
CVE: NA

-------------------------------------------------

In probe_gdrom(), the buffer pointed by 'gd.cd_info' is allocated through
kzalloc() and is used to hold the information of the gdrom device. To
register and unregister the device, the pointer 'gd.cd_info' is passed to
the functions register_cdrom() and unregister_cdrom(), respectively.
However, this buffer is not freed after it is used, which can cause a
memory leak bug.

This patch simply frees the buffer 'gd.cd_info' in exit_gdrom() to fix the
above issue.
Signed-off-by: NWenwen Wang <wang6495@umn.edu>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NZhang Dianfang <zhangdianfang@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/cdrom/gdrom.c

@@ -889,6 +889,7 @@ static void __exit exit_gdrom(void)
 	platform_device_unregister(pd);
 	platform_driver_unregister(&gdrom_driver);
 	kfree(gd.toc);
+	kfree(gd.cd_info);
 }
 
 module_init(init_gdrom);