Re: [PATCH 1/3] firmware: arm_scmi: Fix null pointer dereference during fastchannel init

[Cristian Marussi <cristian.marussi@arm.com>]

On Wed, Nov 29, 2023 at 12:27:46PM +0530, Sibi Sankar wrote:
> The scmi_perf_domain_lookup requires the protocol handle to have the
> private data set, which is yet to happen during the fastchannel init
> scenario. This results in a null pointer dereference. Fix this by using
> the pre-populated perf_dom_info to pass on the required information
> instead.
> 
> Call trace:
> scmi_perf_protocol_init+0x434/0x678
> scmi_get_protocol_instance+0x168/0x29c
> scmi_devres_protocol_instance_get+0x50/0xa0
> scmi_devm_protocol_get+0x20/0x50
> scmi_cpufreq_probe+0x34/0xd4
> scmi_dev_probe+0x28/0x3c
> really_probe+0x148/0x2ac
> __driver_probe_device+0x78/0x12c
> driver_probe_device+0x40/0x160
> __device_attach_driver+0xb8/0x134
> bus_for_each_drv+0x80/0xdc
> __device_attach+0xa8/0x1b0
> device_initial_probe+0x14/0x20
> bus_probe_device+0xa8/0xac
> device_add+0x5cc/0x778
> device_register+0x20/0x30
> __scmi_device_create.part.0+0xec/0x1cc
> scmi_device_create+0x180/0x1c4
> scmi_create_protocol_devices+0x4c/0xb0
> scmi_probe+0x660/0x738
> platform_probe+0x68/0xdc
> really_probe+0x148/0x2ac
> __driver_probe_device+0x78/0x12c
> driver_probe_device+0x40/0x160
> __device_attach_driver+0xb8/0x134
> bus_for_each_drv+0x80/0xdc
> __device_attach+0xa8/0x1b0
> device_initial_probe+0x14/0x20
> bus_probe_device+0xa8/0xac
> deferred_probe_work_func+0x88/0xc0
> process_one_work+0x13c/0x264
> worker_thread+0x32c/0x438
> kthread+0x118/0x11c
> ret_from_fork+0x10/0x20
> 
> Fixes: 619bc6e034f3 ("firmware: arm_scmi: Populate fastchannel info only if set operations are allowed")
> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
> ---

Yes indeed, I made this same error in the past and then I missed it when
reviewing the offending patch :< ...

Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>

Thanks,
Cristian

>  drivers/firmware/arm_scmi/perf.c | 19 +++++++------------
>  1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
> index d1323c5d9c27..a648521e04a3 100644
> --- a/drivers/firmware/arm_scmi/perf.c
> +++ b/drivers/firmware/arm_scmi/perf.c
> @@ -759,40 +759,35 @@ static int scmi_perf_level_limits_notify(const struct scmi_protocol_handle *ph,
>  }
>  
>  static void scmi_perf_domain_init_fc(const struct scmi_protocol_handle *ph,
> -				     u32 domain, struct scmi_fc_info **p_fc)
> +				     struct perf_dom_info *dom)
>  {
>  	struct scmi_fc_info *fc;
> -	struct perf_dom_info *dom;
> -
> -	dom = scmi_perf_domain_lookup(ph, domain);
> -	if (IS_ERR(dom))
> -		return;
>  
>  	fc = devm_kcalloc(ph->dev, PERF_FC_MAX, sizeof(*fc), GFP_KERNEL);
>  	if (!fc)
>  		return;
>  
>  	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
> -				   PERF_LEVEL_GET, 4, domain,
> +				   PERF_LEVEL_GET, 4, dom->id,
>  				   &fc[PERF_FC_LEVEL].get_addr, NULL);
>  
>  	ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
> -				   PERF_LIMITS_GET, 8, domain,
> +				   PERF_LIMITS_GET, 8, dom->id,
>  				   &fc[PERF_FC_LIMIT].get_addr, NULL);
>  
>  	if (dom->info.set_perf)
>  		ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
> -					   PERF_LEVEL_SET, 4, domain,
> +					   PERF_LEVEL_SET, 4, dom->id,
>  					   &fc[PERF_FC_LEVEL].set_addr,
>  					   &fc[PERF_FC_LEVEL].set_db);
>  
>  	if (dom->set_limits)
>  		ph->hops->fastchannel_init(ph, PERF_DESCRIBE_FASTCHANNEL,
> -					   PERF_LIMITS_SET, 8, domain,
> +					   PERF_LIMITS_SET, 8, dom->id,
>  					   &fc[PERF_FC_LIMIT].set_addr,
>  					   &fc[PERF_FC_LIMIT].set_db);
>  
> -	*p_fc = fc;
> +	dom->fc_info = fc;
>  }
>  
>  static int scmi_dvfs_device_opps_add(const struct scmi_protocol_handle *ph,
> @@ -1102,7 +1097,7 @@ static int scmi_perf_protocol_init(const struct scmi_protocol_handle *ph)
>  		scmi_perf_describe_levels_get(ph, dom, version);
>  
>  		if (dom->perf_fastchannels)
> -			scmi_perf_domain_init_fc(ph, dom->id, &dom->fc_info);
> +			scmi_perf_domain_init_fc(ph, dom);
>  	}
>  
>  	ret = devm_add_action_or_reset(ph->dev, scmi_perf_xa_destroy, pinfo);
> -- 
> 2.17.1
>