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

Hi Jiri and Benjamin,

Looping you in for this v2. Apologies for the oversight in the To list.

Thanks,
Ryan
> -----Original Message-----
> From: Lin, Ryan <ryan.lin@intel.com>
> Sent: Friday, January 30, 2026 1:35 PM
> To: linux-kernel@vger.kernel.org; linux-input@vger.kernel.org;
> srinivas.pandruvada@linux.intel.com; Zhang, Lixu <lixu.zhang@intel.com>
> Cc: Lin, Ryan <ryan.lin@intel.com>
> Subject: [PATCH v2] HID: intel-ish-hid: fix NULL-ptr-deref in
> ishtp_bus_remove_all_clients
> 
> 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 Sat, 31 Jan 2026, Lin, Ryan wrote:

> Hi Jiri and Benjamin,
> 
> Looping you in for this v2. Apologies for the oversight in the To list.

Thanks for fixing that up. I've now queued the patch.

-- 
Jiri Kosina
SUSE Labs