[PATCH] drm/bridge: megachips: Fix error handling in i2c_register_driver()

[Yuan Can]

在 2022/11/8 16:50, Andrzej Hajda 写道:
>
>
> On 08.11.2022 09:29, Yuan Can wrote:
>> A problem about insmod megachips-stdpxxxx-ge-b850v3-fw.ko failed is
>> triggered with the following log given:
>>
>> [ 4497.981497] Error: Driver 'stdp4028-ge-b850v3-fw' is already 
>> registered, aborting...
>> insmod: ERROR: could not insert module 
>> megachips-stdpxxxx-ge-b850v3-fw.ko: Device or resource busy
>>
>> The reason is that stdpxxxx_ge_b850v3_init() returns i2c_add_driver()
>> directly without checking its return value, if i2c_add_driver() failed,
>> it returns without calling i2c_del_driver() on the previous i2c driver,
>> resulting the megachips-stdpxxxx-ge-b850v3-fw can never be installed
>> later.
>> A simple call graph is shown as below:
>>
>>   stdpxxxx_ge_b850v3_init()
>>     i2c_add_driver(&stdp4028_ge_b850v3_fw_driver)
>>     i2c_add_driver(&stdp2690_ge_b850v3_fw_driver)
>>       i2c_register_driver()
>>         driver_register()
>>           bus_add_driver()
>>             priv = kzalloc(...) # OOM happened
>>     # return without delete stdp4028_ge_b850v3_fw_driver
>>
>> Fix by calling i2c_del_driver() on stdp4028_ge_b850v3_fw_driver when
>> i2c_add_driver() returns error.
>>
>> Fixes: fcfa0ddc18ed ("drm/bridge: Drivers for 
>> megachips-stdpxxxx-ge-b850v3-fw (LVDS-DP++)")
>> Signed-off-by: Yuan Can <yuancan at huawei.com>
>> ---
>>   drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c | 8 +++++++-
>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c 
>> b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
>> index 97359f807bfc..0d037eeefcf3 100644
>> --- a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
>> +++ b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
>> @@ -440,7 +440,13 @@ static int __init stdpxxxx_ge_b850v3_init(void)
>>       if (ret)
>>           return ret;
>>   -    return i2c_add_driver(&stdp2690_ge_b850v3_fw_driver);
>> +    ret = i2c_add_driver(&stdp2690_ge_b850v3_fw_driver);
>> +    if (ret) {
>> +        i2c_del_driver(&stdp4028_ge_b850v3_fw_driver);
>> +        return ret;
>> +    }
>> +
>> +    return 0;
>
> Could be:
> ret = i2c_add_driver(&stdp2690_ge_b850v3_fw_driver);
> if (ret)
>     i2c_del_driver(&stdp4028_ge_b850v3_fw_driver);
> return ret;
>
> Up to you. Anyway:
> Reviewed-by: Andrzej Hajda <andrzej.hajda at intel.com>
Thanks for your suggestion, I will change to this style with your 
Reviewed-by in the v2 patch.

-- 
Best regards,
Yuan Can