scsi: target: Fix NULL pointer dereference in core_scsi3_decode_spec_i_port()

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

scsi: target: Fix NULL pointer dereference in core_scsi3_decode_spec_i_port()

The function core_scsi3_decode_spec_i_port(), in its error code path, unconditionally calls core_scsi3_lunacl_undepend_item() passing the dest_se_deve pointer, which may be NULL.

This can lead to a NULL pointer dereference if dest_se_deve remains unset.

SPC-3 PR SPEC_I_PT: Unable to locate dest_tpg Unable to handle kernel paging request at virtual address dfff800000000012 Call trace: core_scsi3_lunacl_undepend_item+0x2c/0xf0 [target_core_mod] (P) core_scsi3_decode_spec_i_port+0x120c/0x1c30 [target_core_mod] core_scsi3_emulate_pro_register+0x6b8/0xcd8 [target_core_mod] target_scsi3_emulate_pr_out+0x56c/0x840 [target_core_mod]

Fix this by adding a NULL check before calling core_scsi3_lunacl_undepend_item()