From: Tuo Li <islituo@gmail.com>
Date: Thu, 25 Dec 2025 13:03:26 +0000 (+0800)
Subject: md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()
X-Git-Tag: v6.12.64~230
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=20597b7229aea8b5bc45cd92097640257c7fc33b;p=thirdparty%2Fkernel%2Fstable.git

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

[ Upstream commit 7ad6ef91d8745d04aff9cce7bdbc6320d8e05fe9 ]

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 <islituo@gmail.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Link: https://lore.kernel.org/linux-raid/20251225130326.67780-1-islituo@gmail.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 8e5ccca3b68b8..7262b77a8e022 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7181,12 +7181,14 @@ 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);