scsi: iscsi: Fix iscsi_task use after free

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: scsi: iscsi: Fix iscsi_task use after free Commit d39df158518c ("scsi: iscsi: Have abort handler get ref to conn") added iscsi_get_conn()/iscsi_put_conn() calls during abort handling but then also changed the handling of the case where we detect an already completed task where we now end up doing a goto to the common put/cleanup code. This results in a iscsi_task use after free, because the common cleanup code will do a put on the iscsi_task. This reverts the goto and moves the iscsi_get_conn() to after we've checked if the iscsi_task is valid.

References

• https://git.kernel.org/stable/c/1642f51ac0d4f2b55d5748094c49ff8f7191b93c
• https://git.kernel.org/stable/c/258aad75c62146453d03028a44f2f1590d58e1f6