mtd: Fix gluebi NULL pointer dereference caused by ftl notifier

In the Linux kernel, the following vulnerability has been resolved:

mtd: Fix gluebi NULL pointer dereference caused by ftl notifier

If both ftl.ko and gluebi.ko are loaded, the notifier of ftl

triggers NULL pointer dereference when trying to access

‘gluebi->desc’ in gluebi_read().

ubi_gluebi_init

ubi_register_volume_notifier

ubi_enumerate_volumes

ubi_notify_all

gluebi_notify nb->notifier_call()

gluebi_create

mtd_device_register

mtd_device_parse_register

add_mtd_device

blktrans_notify_add not->add()

ftl_add_mtd tr->add_mtd()

scan_header

mtd_read

mtd_read_oob

mtd_read_oob_std

gluebi_read mtd->read()

gluebi->desc - NULL

Detailed reproduction information available at the Link [1],

In the normal case, obtain gluebi->desc in the gluebi_get_device(),

and access gluebi->desc in the gluebi_read(). However,

gluebi_get_device() is not executed in advance in the

ftl_add_mtd() process, which leads to NULL pointer dereference.

The solution for the gluebi module is to run jffs2 on the UBI

volume without considering working with ftl or mtdblock [2].

Therefore, this problem can be avoided by preventing gluebi from

creating the mtdblock device after creating mtd partition of the

type MTD_UBIVOLUME.