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

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()

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Link: https://lore.kernel.org/r/20250612101556.24829-1-mlombard@redhat.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: John Meneghini <jmeneghi@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>