In the Linux kernel, the following vulnerability has been resolved: scsi: target: iblock: Fix wrong PR ops NULL check for PREEMPT/RELEASE

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

scsi: target: iblock: Fix wrong PR ops NULL check for PREEMPT/RELEASE

In the iblock_execute_pr_out() function, PRO_PREEMPT,
PRO_PREEMPT_AND_ABORT, and PRO_RELEASE all perform callback capability
checks through ops->pr_clear. The error check allows unimplemented hooks
to pass through the gate, resulting dereferencing a NULL function
pointer.

Check whether the hooks that need to be called are supported.