[PATCH 3.16.y-ckt 73/94] mvsas: Fix NULL pointer dereference in mvs_slot_task_free

[Luis Henriques]

3.16.7-ckt20 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: =?UTF-8?q?D=C4=81vis=20Mos=C4=81ns?= <davispuh at gmail.com>

commit 2280521719e81919283b82902ac24058f87dfc1b 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=101891
Signed-off-by: Dāvis Mosāns <davispuh at gmail.com>
Reviewed-by: Tomas Henzl <thenzl at redhat.com>
Reviewed-by: Johannes Thumshirn <jthumshirn at suse.de>
Signed-off-by: James Bottomley <JBottomley at Odin.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/scsi/mvsas/mv_sas.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/mvsas/mv_sas.c b/drivers/scsi/mvsas/mv_sas.c
index 4c0b8b4e1d40..42b1f3318e59 100644
--- a/drivers/scsi/mvsas/mv_sas.c
+++ b/drivers/scsi/mvsas/mv_sas.c
@@ -988,6 +988,8 @@ 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))