dm mpath: fix uninitialized 'pg_init_wait' waitqueue_head NULL pointer

Initialize all the scsi_dh related 'struct multipath' members regardless
of whether a scsi_dh is in use or not.

The subtle (and fragile) SCSI-assuming legacy code clearly needs further
decoupling from non-SCSI (and/or developer understanding).

Fixes: 8d47e65948dd ("dm mpath: remove unnecessary NVMe branching in favor of scsi_dh checks")
Reported-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 10 insertions, 11 deletions

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 3fde9e9faddd..87c404eebe9f 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -223,6 +223,16 @@ static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 
         dm_table_set_type(ti->table, m->queue_mode);
 
+        /*
+         * Init fields that are only used when a scsi_dh is attached
+         * - must do this unconditionally (really doesn't hurt non-SCSI uses)
+         */
+        set_bit(MPATHF_QUEUE_IO, &m->flags);
+        atomic_set(&m->pg_init_in_progress, 0);
+        atomic_set(&m->pg_init_count, 0);
+        m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
+        init_waitqueue_head(&m->pg_init_wait);
+
         return 0;
 }
 
@@ -331,7 +341,6 @@ static void __switch_pg(struct multipath *m, struct priority_group *pg)
                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
                 set_bit(MPATHF_QUEUE_IO, &m->flags);
         } else {
-                /* FIXME: not needed if no scsi_dh is attached */
                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
         }
@@ -823,16 +832,6 @@ retain:
                          */
                         kfree(m->hw_handler_name);
                         m->hw_handler_name = attached_handler_name;
-
-                        /*
-                         * Init fields that are only used when a scsi_dh is attached
-                         */
-                        if (!test_and_set_bit(MPATHF_QUEUE_IO, &m->flags)) {
-                                atomic_set(&m->pg_init_in_progress, 0);
-                                atomic_set(&m->pg_init_count, 0);
-                                m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
-                                init_waitqueue_head(&m->pg_init_wait);
-                        }
                 }
         }