mvsas: Fix NULL pointer dereference in mvs_slot_task_free

commit 22805217 upstream.

When pci_pool_alloc fails in mvs_task_prep then task->lldd_task stays
NULL but it's later used in mvs_abort_task as slot which is passed
to mvs_slot_task_free causing NULL pointer dereference.

Just return from mvs_slot_task_free when passed with NULL slot.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=101891Signed-off-by: Dāvis Mosāns <davispuh@gmail.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/scsi/mvsas/mv_sas.c

@@ -991,6 +991,8 @@ static void mvs_slot_free(struct mvs_info *mvi, u32 rx_desc)
 static void mvs_slot_task_free(struct mvs_info *mvi, struct sas_task *task,
 			  struct mvs_slot_info *slot, u32 slot_idx)
 {
+	if (!slot)
+		return;
 	if (!slot->task)
 		return;
 	if (!sas_protocol_ata(task->task_proto))