[PATCH 6.12 338/567] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

Greg Kroah-Hartman
2026-01-06T17:32:57Z

From: Tuo Li <islituo@gmail.com>

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

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 8e5ccca3b68b..7262b77a8e02 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);
--
2.51.0