Re: [PATCH 1/2] soc: xilinx: Fix race condition in event registration

[Michal Simek <michal.simek@amd.com>]

On 3/17/26 14:34, Prasanna Kumar T S M wrote:
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> 
> The zynqmp_power driver registers handlers for suspend and subsystem
> restart events using register_event(). However, the work structures
> (zynqmp_pm_init_suspend_work and zynqmp_pm_init_restart_work) used by
> these handlers were allocated and initialized after the registration
> call.
> 
> This created a race window where, if the firmware triggered an event
> immediately after registration but before allocation, the callback
> (suspend_event_callback or subsystem_restart_event_callback) would
> dereference a NULL pointer in work_pending(), leading to a crash.
> 
> Fix this by allocating and initializing the work structures before
> registering the events.
> 
> Fixes: fcf544ac6439 ("soc: xilinx: Add cb event for subsystem restart")
> 

please remove empty line above.

> Signed-off-by: Prasanna Kumar T S M <ptsm@linux.microsoft.com>
> ---
>   drivers/soc/xilinx/zynqmp_power.c | 34 +++++++++++++++----------------
>   1 file changed, 17 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/soc/xilinx/zynqmp_power.c b/drivers/soc/xilinx/zynqmp_power.c
> index 9085db1b480a..aa35b63b45a3 100644
> --- a/drivers/soc/xilinx/zynqmp_power.c
> +++ b/drivers/soc/xilinx/zynqmp_power.c
> @@ -303,18 +303,18 @@ static int zynqmp_pm_probe(struct platform_device *pdev)
>           * is not available to use) or -ENODEV(Xilinx Event Manager not compiled),
>           * then use ipi-mailbox or interrupt method.
>           */
> +       zynqmp_pm_init_suspend_work = devm_kzalloc(&pdev->dev,
> +                                                  sizeof(struct zynqmp_pm_work_struct),
> +                                                  GFP_KERNEL);
> +       if (!zynqmp_pm_init_suspend_work)
> +               return -ENOMEM;
> +
> +       INIT_WORK(&zynqmp_pm_init_suspend_work->callback_work,
> +                 zynqmp_pm_init_suspend_work_fn);
> +
>          ret = register_event(&pdev->dev, PM_INIT_SUSPEND_CB, 0, 0, false,
>                               suspend_event_callback);
>          if (!ret) {
> -               zynqmp_pm_init_suspend_work = devm_kzalloc(&pdev->dev,
> -                                                          sizeof(struct zynqmp_pm_work_struct),
> -                                                          GFP_KERNEL);
> -               if (!zynqmp_pm_init_suspend_work)
> -                       return -ENOMEM;
> -
> -               INIT_WORK(&zynqmp_pm_init_suspend_work->callback_work,
> -                         zynqmp_pm_init_suspend_work_fn);
> -
>                  ret = zynqmp_pm_get_family_info(&pm_family_code);
>                  if (ret < 0)
>                          return ret;
> @@ -326,14 +326,6 @@ static int zynqmp_pm_probe(struct platform_device *pdev)
>                  else
>                          return -ENODEV;
> 
> -               ret = register_event(&pdev->dev, PM_NOTIFY_CB, node_id, EVENT_SUBSYSTEM_RESTART,
> -                                    false, subsystem_restart_event_callback);
> -               if (ret) {
> -                       dev_err(&pdev->dev, "Failed to Register with Xilinx Event manager %d\n",
> -                               ret);
> -                       return ret;
> -               }
> -
>                  zynqmp_pm_init_restart_work = devm_kzalloc(&pdev->dev,
>                                                             sizeof(struct zynqmp_pm_work_struct),
>                                                             GFP_KERNEL);
> @@ -342,6 +334,14 @@ static int zynqmp_pm_probe(struct platform_device *pdev)
> 
>                  INIT_WORK(&zynqmp_pm_init_restart_work->callback_work,
>                            zynqmp_pm_subsystem_restart_work_fn);
> +
> +               ret = register_event(&pdev->dev, PM_NOTIFY_CB, node_id, EVENT_SUBSYSTEM_RESTART,
> +                                    false, subsystem_restart_event_callback);
> +               if (ret) {
> +                       dev_err(&pdev->dev, "Failed to Register with Xilinx Event manager %d\n",
> +                               ret);
> +                       return ret;
> +               }
>          } else if (ret != -EACCES && ret != -ENODEV) {
>                  dev_err(&pdev->dev, "Failed to Register with Xilinx Event manager %d\n", ret);
>                  return ret;
> --
> 2.49.0
> 


the same change should happen also for
  else if (of_property_present(pdev->dev.of_node, "mboxes")) {


diff --git a/drivers/soc/xilinx/zynqmp_power.c b/drivers/soc/xilinx/zynqmp_power.c
index 5086c1e6797e..98bac07f73d1 100644
--- a/drivers/soc/xilinx/zynqmp_power.c
+++ b/drivers/soc/xilinx/zynqmp_power.c
@@ -346,15 +346,6 @@ static int zynqmp_pm_probe(struct platform_device *pdev)
                 dev_err(&pdev->dev, "Failed to Register with Xilinx Event 
manager %d\n", ret);
                 return ret;
         } else if (of_property_present(pdev->dev.of_node, "mboxes")) {
-               zynqmp_pm_init_suspend_work =
-                       devm_kzalloc(&pdev->dev,
-                                    sizeof(struct zynqmp_pm_work_struct),
-                                    GFP_KERNEL);
-               if (!zynqmp_pm_init_suspend_work)
-                       return -ENOMEM;
-
-               INIT_WORK(&zynqmp_pm_init_suspend_work->callback_work,
-                         zynqmp_pm_init_suspend_work_fn);
                 client = devm_kzalloc(&pdev->dev, sizeof(*client), GFP_KERNEL);
                 if (!client)
                         return -ENOMEM;

Thanks,
Michal