Re: [PATCH 2/2] remoteproc: qcom: Check glink->edge in glink_subdev_stop()

[Jingyi Wang <jingyi.wang@oss.qualcomm.com>]

On 4/10/2026 10:15 PM, Stephan Gerhold wrote:
> On Thu, Apr 09, 2026 at 01:46:22AM -0700, Jingyi Wang wrote:
>> For rproc that doing attach, glink_subdev_start() is called only when
>> attach successfully. If rproc_report_crash() is called in the attach
>> function, rproc_boot_recovery()->rproc_stop()->glink_subdev_stop() could
>> be called and cause NULL pointer dereference:
>>
>>   Unable to handle kernel NULL pointer dereference at virtual address 0000000000000300
>>   Mem abort info:
>>   ...
>>   pc : qcom_glink_smem_unregister+0x14/0x48 [qcom_glink_smem]
>>   lr : glink_subdev_stop+0x1c/0x30 [qcom_common]
>>   ...
>>   Call trace:
>>    qcom_glink_smem_unregister+0x14/0x48 [qcom_glink_smem] (P)
>>    glink_subdev_stop+0x1c/0x30 [qcom_common]
>>    rproc_stop+0x58/0x17c
>>    rproc_trigger_recovery+0xb0/0x150
>>    rproc_crash_handler_work+0xa4/0xc4
>>    process_scheduled_works+0x18c/0x2d8
>>    worker_thread+0x144/0x280
>>    kthread+0x124/0x138
>>    ret_from_fork+0x10/0x20
>>   Code: a9be7bfd 910003fd a90153f3 aa0003f3 (b9430000)
>>   ---[ end trace 0000000000000000 ]---
>>
>> Add NULL pointer check in the glink_subdev_stop() to make sure
>> qcom_glink_smem_unregister() will not be called if glink_subdev_start()
>> is not called.
>>
> 
> You mention the actual root problem here: Why is glink_subdev_stop()
> called if glink_subdev_start() wasn't called?
> 
> The call to rproc_start_subdevices() in __rproc_attach() makes sure that
> all subdevices are in consistent state when exiting the function (either
> prepared+started or stopped+unprepared). Only if all subdevices were
> started successfully, the rproc->state is changed to RPROC_ATTACHED.
> 
> In your case, attaching the rproc failed so the rproc->state should be
> still RPROC_DETACHED. All subdevices should be stopped+unprepared. We
> shouldn't stop/unprepare any subdevices again in this state, they all
> might crash like glink does here.
> 
> We know that subdevices are already stopped+unprepared in RPROC_DETACHED
> state, so I think you just need to skip rproc_stop_subdevices() and
> rproc_unprepare_subdevices() inside rproc_stop() in this case, see diff
> below.
> 
> Thanks,
> Stephan
> 
> @@ -1708,8 +1709,9 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
>   	if (!rproc->ops->stop)
>   		return -EINVAL;
>   
> -	/* Stop any subdevices for the remote processor */
> -	rproc_stop_subdevices(rproc, crashed);
> +	/* Stop any subdevices for the remote processor if it was attached */
> +	if (rproc->state != RPROC_DETACHED)
> +		rproc_stop_subdevices(rproc, crashed);
>   
>   	/* the installed resource table is no longer accessible */
>   	ret = rproc_reset_rsc_table_on_stop(rproc);
> @@ -1726,7 +1728,8 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
>   		return ret;
>   	}
>   
> -	rproc_unprepare_subdevices(rproc);
> +	if (rproc->state != RPROC_DETACHED)
> +		rproc_unprepare_subdevices(rproc);
>   
>   	rproc->state = RPROC_OFFLINE;
>   

Hi Stephen,

In this case, rproc_crash_handler_work()->rproc_trigger_recovery()->
rproc_boot_recovery()->rproc_stop()->glink_subdev_stop() is called,
"rproc->state = RPROC_CRASHED" is set in the rproc_crash_handler_work
before rproc_boot_recovery is called, so checking RPROC_DETACHED can
not work for this case.

Thanks,
Jingyi