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

Jingyi Wang
2026-04-14T03:23:57Z

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