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SubjectRe: [PATCH] atmel: fix an error handle in mxt_probe
HI, Dmitry
thanks for your reply :)

On 2015年05月14日 01:41, Dmitry Torokhov wrote:
> Hi,
>
> On Wed, Apr 22, 2015 at 06:46:58PM +0800, Pan Xinhui wrote:
>> mxt_probe() may fail at last step, and the queue_work scheduled by request_firmware_nowait
>> may run later and then access some data which is freed.
>> To handle this error, add one mutex_lock to cover such case. It may cause module load delay only when the probe fails.
>>
>> here is the detail.
>>
>> module load: worker_thread:
>> mxt_probe -> mxt_initialize -> request_firmware_nowait (schedule_work)
>> |
>> sysfs_create_group (fails) mxt_config_cb -> mxt_configure_objects (may access data freed)
>> |
>> err_free_object: some cleanup work, like free(data).
>>
>> Signed-off-by: xinhuix.pan <xinhuix.pan@intel.com>
>> ---
>> drivers/input/touchscreen/atmel_mxt_ts.c | 14 ++++++++++++++
>> 1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
>> index 2875ddf..af057c0 100644
>> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
>> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
>> @@ -1978,10 +1978,19 @@ err_free_mem:
>> static int mxt_configure_objects(struct mxt_data *data,
>> const struct firmware *cfg);
>> +static DEFINE_MUTEX(err_probe_lock);
>> +static int err_probe;
>
> While you are right that bad things will happen if we let
> request_firmware_nowait() run after driver fails to bind to the device
> using statics to indicate success or failure is not good idea since you
> may have several such devices in your unit. Also it still doe snot help
> if you decide to unbind the device quickly or unlock the module.
>
> I guess the best way is to signal a completion from callback and wait
> for it in error path and in remove().
>
> Thanks.
>

yes, statics is not good.
It's also a good point that do some work both in err patch and in_remove().

thanks for your nice advices. I will work out patch V2.

thanks

xinhui

>> +
>> static void mxt_config_cb(const struct firmware *cfg, void *ctx)
>> {
>> + mutex_lock(&err_probe_lock);
>> + if (err_probe) {
>> + mutex_unlock(&err_probe_lock);
>> + return;
>> + }
>> mxt_configure_objects(ctx, cfg);
>> release_firmware(cfg);
>> + mutex_unlock(&err_probe_lock);
>> }
>> static int mxt_initialize(struct mxt_data *data)
>> @@ -2423,6 +2432,8 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
>> const struct mxt_platform_data *pdata;
>> int error;
>> + err_probe = 0;
>> +
>> pdata = dev_get_platdata(&client->dev);
>> if (!pdata) {
>> pdata = mxt_parse_dt(client);
>> @@ -2472,6 +2483,9 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
>> return 0;
>> err_free_object:
>> + mutex_lock(&err_probe_lock);
>> + err_probe = -1;
>> + mutex_unlock(&err_probe_lock);
>> mxt_free_input_device(data);
>> mxt_free_object_table(data);
>> err_free_irq:
>> --
>> 1.9.1
>


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