On 4/14/2026 4:27 PM, Stephan Gerhold wrote:
On Tue, Apr 14, 2026 at 11:23:50AM +0800, Jingyi Wang wrote:
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.
@@ -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;
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.
You're right, I forgot about that. I think we need a more generic
solution for this though. rproc_stop_subdevices() should not be called
without a prior call to rproc_start_subdevices().
I think there are a couple of options for this:
- Add a bool "subdevs_started" to struct rproc and manage that
separately from the rproc->state.
- Track the rproc state before the crash separately (something like
rproc->state_before_crash) and check that in the stop path.
- Add a new state RPROC_CRASHED_DETACHED to make sure the states are
unique.
- ...
Sure, I think a bool like subdevs_started will be better for maintain?
Does the same issue also exist in qcom_pas_stop() of "[PATCH v5 4/5]
remoteproc: qcom: pas: Add late attach support for subsystems" [1]?
There you check for pas->rproc->state != RPROC_ATTACHED, wouldn't this
also fail for the RPROC_CRASHED case?
I tested calling rproc_report_crash directly during qcom_pas_attach but
did not see issue, handover_issued is set only if attach is success
so "handover = qcom_q6v5_unprepare(&pas->q6v5);" will return false and
"qcom_pas_handover(&pas->q6v5);" will not be called.
Thanks,
Jingyi
Thanks,
Stephan
[1]:
https://lore.kernel.org/linux-arm-msm/[email protected]/
