Re: [PATCH net] net: wwan: iosm: fix NULL pointer dereference when removing device

[Simon Horman <simon.horman@corigine.com>]

On Thu, May 11, 2023 at 03:34:44PM +0530, m.chetan.kumar@linux.intel.com wrote:
> From: M Chetan Kumar <m.chetan.kumar@linux.intel.com>
> 
> In suspend and resume cycle, the removal and rescan of device ends
> up in NULL pointer dereference.
> 
> During driver initialization, if the ipc_imem_wwan_channel_init()
> fails to get the valid device capabilities it returns an error and
> further no resource (wwan struct) will be allocated. Now in this
> situation if driver removal procedure is initiated it would result
> in NULL pointer exception since unallocated wwan struct is dereferenced
> inside ipc_wwan_deinit().
> 
> ipc_imem_run_state_worker() to handle the called functions return value
> and to release the resource in failure case. It also reports the link
> down event in failure cases. The user space application can handle this
> event to do a device reset for restoring the device communication.
> 
> Fixes: 3670970dd8c6 ("net: iosm: shared memory IPC interface")
> Reported-by: Samuel Wein PhD <sam@samwein.com>
> Closes: https://lore.kernel.org/netdev/20230427140819.1310f4bd@kernel.org/T/
> Signed-off-by: M Chetan Kumar <m.chetan.kumar@linux.intel.com>

...

> @@ -622,6 +630,15 @@ static void ipc_imem_run_state_worker(struct work_struct *instance)
>  
>  	/* Complete all memory stores after setting bit */
>  	smp_mb__after_atomic();
> +
> +	return;
> +
> +err_channel_init:
> +	ipc_mux_deinit(ipc_imem->mux);
> +err_mux_init:
> +err_cap_init:
> +err_cp_phase:
> +	ipc_uevent_send(ipc_imem->dev, UEVENT_CD_READY_LINK_DOWN);

Hi Chentan,

Thanks for your patch.
a nit from my side.

I think it is preferable for labels to be named after what they do
rather than where they are called from.

Something like:

err_mux_deinit:
	ipc_mux_deinit(ipc_imem->mux);
err_out:
	ipc_uevent_send(ipc_imem->dev, UEVENT_CD_READY_LINK_DOWN);

I also note that if ipc_mux_deinit() checked for a NULL (and did nothing),
then this could become:

err_out:
	ipc_mux_deinit(ipc_imem->mux);
	ipc_uevent_send(ipc_imem->dev, UEVENT_CD_READY_LINK_DOWN);

>  }
>  

...