In the Linux kernel, the following vulnerability has been resolved:
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().