ubi: Fix possible null-ptr-deref in ubi_free_volume()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: ubi: Fix possible null-ptr-deref in ubi_free_volume() It willl cause null-ptr-deref in the following case: uif_init() ubi_add_volume() cdev_add() -> if it fails, call kill_volumes() device_register() kill_volumes() -> if ubi_add_volume() fails call this function ubi_free_volume() cdev_del() device_unregister() -> trying to delete a not added device, it causes null-ptr-deref So in ubi_free_volume(), it delete devices whether they are added or not, it will causes null-ptr-deref. Handle the error case whlie calling ubi_add_volume() to fix this problem. If add volume fails, set the corresponding vol to null, so it can not be accessed in kill_volumes() and release the resource in ubi_add_volume() error path.

References

• https://git.kernel.org/stable/c/5558bcf1c58720ca6e9d6198d921cb3aa337f038
• https://git.kernel.org/stable/c/45b2c5ca4d2edae70f19fdb086bd927840c4c309
• https://git.kernel.org/stable/c/234c53e57424992e657e6f4acc00d3df0983176f
• https://git.kernel.org/stable/c/fcbc795abe7897da4b5d2a6ab5010e36774b00c2
• https://git.kernel.org/stable/c/5ec4c8aca5a221756a9007deadfea92795319fee
• https://git.kernel.org/stable/c/2ea7195b195009ecf0046e55361f393ba96d02db
• https://git.kernel.org/stable/c/9eccdb0760cbcb4427b5303a83a3007de998af51
• https://git.kernel.org/stable/c/c15859bfd326c10230f09cb48a17f8a35f190342