md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

The variable mddev->private is first assigned to conf and then checked:

   conf = mddev->private;
    if (!conf) ...

If conf is NULL, then mddev->private is also NULL. In this case, null-pointer dereferences can occur when calling raid5_quiesce():

  raid5_quiesce(mddev, true);
  raid5_quiesce(mddev, false);

since mddev->private is assigned to conf again in raid5_quiesce(), and conf is dereferenced in several places, for example:

  conf->quiesce = 0;
  wake_up(&conf->wait_for_quiescent);

To fix this issue, the function should unlock mddev and return before invoking raid5_quiesce() when conf is NULL, following the existing pattern in raid5_change_consistency_policy().

Fixes fa1944bbe622 ("md/raid5: Wait sync io to finish before changing group cnt")

Signed-off-by Tuo Li <[email protected]>

---
v2:
* Move the NULL check and early return ahead of the first call to raid5_quiesce().
Thanks to Yu Kuai for helpful advice.

---
 drivers/md/raid5.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

drivers/md/raid5.c +6 -5

index e57ce3295292..8dc98f545969 100644
@@ -7187,12 +7187,14 @@ raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
        err = mddev_suspend_and_lock(mddev);
        if (err)
                return err;
+       conf = mddev->private;
+       if (!conf) {
+               mddev_unlock_and_resume(mddev);
+               return -ENODEV;
+       }
        raid5_quiesce(mddev, true);
 
-       conf = mddev->private;
-       if (!conf)
-               err = -ENODEV;
-       else if (new != conf->worker_cnt_per_group) {
+       if (new != conf->worker_cnt_per_group) {
                old_groups = conf->worker_groups;
                if (old_groups)
                        flush_workqueue(raid5_wq);
--

2.43.0

The variable mddev->private is first assigned to conf and then checked:

    conf = mddev->private;
     if (!conf) ...

If conf is NULL, then mddev->private is also NULL. In this case, null-pointer dereferences can occur when calling raid5_quiesce():

   raid5_quiesce(mddev, true);
   raid5_quiesce(mddev, false);

since mddev->private is assigned to conf again in raid5_quiesce(), and conf is dereferenced in several places, for example:

   conf->quiesce = 0;
   wake_up(&conf->wait_for_quiescent);

To fix this issue, the function should unlock mddev and return before invoking raid5_quiesce() when conf is NULL, following the existing pattern in raid5_change_consistency_policy().

Fixes fa1944bbe622 ("md/raid5: Wait sync io to finish before changing group cnt")

Signed-off-by Tuo Li <[email protected]>

---
v2:
* Move the NULL check and early return ahead of the first call to raid5_quiesce().
Thanks to Yu Kuai for helpful advice.

---
  drivers/md/raid5.c | 10 ++++++----
  1 file changed, 6 insertions(+), 4 deletions(-)

drivers/md/raid5.c +5 -0

index e57ce3295292..8dc98f545969 100644
@@ -7187,12 +7187,14 @@ raid5_store_group_thread_cnt(struct mddev *mddev, const char *page, size_t len)
  	err = mddev_suspend_and_lock(mddev);
  	if (err)
  		return err;
+	conf = mddev->private;
+	if (!conf) {
+		mddev_unlock_and_resume(mddev);
+		return -ENODEV;
+	}

The variable mddev->private is first assigned to conf and then checked:

    conf = mddev->private;
     if (!conf) ...

If conf is NULL, then mddev->private is also NULL. In this case, null-pointer dereferences can occur when calling raid5_quiesce():

   raid5_quiesce(mddev, true);
   raid5_quiesce(mddev, false);

since mddev->private is assigned to conf again in raid5_quiesce(), and conf is dereferenced in several places, for example:

   conf->quiesce = 0;
   wake_up(&conf->wait_for_quiescent);

To fix this issue, the function should unlock mddev and return before invoking raid5_quiesce() when conf is NULL, following the existing pattern in raid5_change_consistency_policy().

Fixes fa1944bbe622 ("md/raid5: Wait sync io to finish before changing group cnt")

Signed-off-by Tuo Li<[email protected]>

---
v2:
* Move the NULL check and early return ahead of the first call to raid5_quiesce().
Thanks to Yu Kuai for helpful advice.

---
  drivers/md/raid5.c | 10 ++++++----
  1 file changed, 6 insertions(+), 4 deletions(-)