During a warm reset flow, the cl->device pointer may be NULL if the
reset occurs while clients are still being enumerated. Accessing
cl->device->reference_count without a NULL check leads to a kernel panic.

This issue was identified during multi-unit warm reboot stress clycles.
Add a defensive NULL check for cl->device to ensure stability under
such intensive testing conditions.

KASAN: null-ptr-deref in range [0000000000000000-0000000000000007]
Workqueue: ish_fw_update_wq fw_reset_work_fn

Call Trace:
 ishtp_bus_remove_all_clients+0xbe/0x130 [intel_ishtp]
 ishtp_reset_handler+0x85/0x1a0 [intel_ishtp]
 fw_reset_work_fn+0x8a/0xc0 [intel_ish_ipc]

Fixes: 3703f53b99e4a ("HID: intel_ish-hid: ISH Transport layer")
Signed-off-by: Ryan Lin <ryan.lin@intel.com>
---
 drivers/hid/intel-ish-hid/ishtp/bus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hid/intel-ish-hid/ishtp/bus.c b/drivers/hid/intel-ish-hid/ishtp/bus.c
index c3915f3a060e..b890fbf97a75 100644
--- a/drivers/hid/intel-ish-hid/ishtp/bus.c
+++ b/drivers/hid/intel-ish-hid/ishtp/bus.c
@@ -730,7 +730,7 @@ void ishtp_bus_remove_all_clients(struct ishtp_device *ishtp_dev,
 	spin_lock_irqsave(&ishtp_dev->cl_list_lock, flags);
 	list_for_each_entry(cl, &ishtp_dev->cl_list, link) {
 		cl->state = ISHTP_CL_DISCONNECTED;
-		if (warm_reset && cl->device->reference_count)
+		if (warm_reset && cl->device && cl->device->reference_count)
 			continue;
 
 		/*
-- 
2.34.1

On Fri, 2026-01-30 at 13:25 +0800, Ryan Lin wrote:
> During a warm reset flow, the cl->device pointer may be NULL if the
> reset occurs while clients are still being enumerated. Accessing
> cl->device->reference_count without a NULL check leads to a kernel
> panic.
> 
> This issue was identified during multi-unit warm reboot stress
> clycles.
> Add a defensive NULL check for cl->device to ensure stability under
> such intensive testing conditions.
> 
> KASAN: null-ptr-deref in range [0000000000000000-0000000000000007]
> Workqueue: ish_fw_update_wq fw_reset_work_fn
> 
> Call Trace:
>  ishtp_bus_remove_all_clients+0xbe/0x130 [intel_ishtp]
>  ishtp_reset_handler+0x85/0x1a0 [intel_ishtp]
>  fw_reset_work_fn+0x8a/0xc0 [intel_ish_ipc]
> 
> Fixes: 3703f53b99e4a ("HID: intel_ish-hid: ISH Transport layer")
> Signed-off-by: Ryan Lin <ryan.lin@intel.com>

You need to use get_maintainer.pl to get all TO and CC list.

You missed 
Jiri Kosina <jikos@kernel.org>
Benjamin Tissoires <bentiss@kernel.org>


> ---
>  drivers/hid/intel-ish-hid/ishtp/bus.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hid/intel-ish-hid/ishtp/bus.c
> b/drivers/hid/intel-ish-hid/ishtp/bus.c
> index c3915f3a060e..b890fbf97a75 100644
> --- a/drivers/hid/intel-ish-hid/ishtp/bus.c
> +++ b/drivers/hid/intel-ish-hid/ishtp/bus.c
> @@ -730,7 +730,7 @@ void ishtp_bus_remove_all_clients(struct
> ishtp_device *ishtp_dev,
>  	spin_lock_irqsave(&ishtp_dev->cl_list_lock, flags);
>  	list_for_each_entry(cl, &ishtp_dev->cl_list, link) {
>  		cl->state = ISHTP_CL_DISCONNECTED;
> -		if (warm_reset && cl->device->reference_count)
> +		if (warm_reset && cl->device && cl->device-
> >reference_count)
>  			continue;
>  
>  		/*

> -----Original Message-----
> From: srinivas pandruvada <srinivas.pandruvada@linux.intel.com>
> Sent: Saturday, January 31, 2026 9:32 AM
> To: Lin, Ryan <ryan.lin@intel.com>; linux-kernel@vger.kernel.org; linux-
> input@vger.kernel.org; linux-drivers-review@eclists.intel.com; Zhang, Lixu
> <lixu.zhang@intel.com>; Benjamin Tissoires <bentiss@kernel.org>; Jiri Kosina
> <jikos@kernel.org>
> Subject: Re: [linux-drivers-review] [PATCH] HID: intel-ish-hid: fix NULL-ptr-deref
> in ishtp_bus_remove_all_clients
> 
> On Fri, 2026-01-30 at 13:25 +0800, Ryan Lin wrote:
> > During a warm reset flow, the cl->device pointer may be NULL if the
> > reset occurs while clients are still being enumerated. Accessing
> > cl->device->reference_count without a NULL check leads to a kernel
> > panic.
> >
> > This issue was identified during multi-unit warm reboot stress
> > clycles.
> > Add a defensive NULL check for cl->device to ensure stability under
> > such intensive testing conditions.
> >
> > KASAN: null-ptr-deref in range [0000000000000000-0000000000000007]
> > Workqueue: ish_fw_update_wq fw_reset_work_fn
> >
> > Call Trace:
> >  ishtp_bus_remove_all_clients+0xbe/0x130 [intel_ishtp]
> >  ishtp_reset_handler+0x85/0x1a0 [intel_ishtp]
> >  fw_reset_work_fn+0x8a/0xc0 [intel_ish_ipc]
> >
> > Fixes: 3703f53b99e4a ("HID: intel_ish-hid: ISH Transport layer")
> > Signed-off-by: Ryan Lin <ryan.lin@intel.com>
> 
> You need to use get_maintainer.pl to get all TO and CC list.
> 
> You missed
> Jiri Kosina <jikos@kernel.org>
> Benjamin Tissoires <bentiss@kernel.org>

Thanks, Srinivas. I've looped Jiri and Benjamin in the v2 thread. Appreciate the heads-up.

Regards,
Ryan
> 
> 
> > ---
> >  drivers/hid/intel-ish-hid/ishtp/bus.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/hid/intel-ish-hid/ishtp/bus.c
> > b/drivers/hid/intel-ish-hid/ishtp/bus.c
> > index c3915f3a060e..b890fbf97a75 100644
> > --- a/drivers/hid/intel-ish-hid/ishtp/bus.c
> > +++ b/drivers/hid/intel-ish-hid/ishtp/bus.c
> > @@ -730,7 +730,7 @@ void ishtp_bus_remove_all_clients(struct
> > ishtp_device *ishtp_dev,
> >  	spin_lock_irqsave(&ishtp_dev->cl_list_lock, flags);
> >  	list_for_each_entry(cl, &ishtp_dev->cl_list, link) {
> >  		cl->state = ISHTP_CL_DISCONNECTED;
> > -		if (warm_reset && cl->device->reference_count)
> > +		if (warm_reset && cl->device && cl->device-
> > >reference_count)
> >  			continue;
> >
> >  		/*