[PATCH v2] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

[PATCH v2] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

[Tuo Li]

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>
---
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(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e57ce3295292..8dc98f545969 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -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

Re: [PATCH v2] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

[Xiao Ni]

On Thu, Dec 25, 2025 at 9:04 PM Tuo Li <islituo@gmail.com> wrote:
>
> 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>
> ---
> 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(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index e57ce3295292..8dc98f545969 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -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
>
>

Thanks for the patch. It looks good to me.

Reviewed-by: Xiao Ni <xni@redhat.com>

Re: [PATCH v2] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

[Paul Menzel]

Dear Tuo,


Thank you for your patch.


Am 25.12.25 um 18:03 schrieb Tuo Li:
> The variable mddev->private is first assigned to conf and then checked:
> 
>     conf = mddev->private;
>      if (!conf) ...

Should you resend, please align conf` and `if`.

> 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>
> ---
> 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(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index e57ce3295292..8dc98f545969 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -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);

Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>


Kind regards,

Paul

Re: [PATCH v2] md/raid5: fix possible null-pointer dereferences in raid5_store_group_thread_cnt()

[Yu Kuai]

在 2025/12/25 21:03, Tuo Li 写道:

> 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>
> ---
> 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(-)

Applied to md-6.19

-- 
Thansk,
Kuai