Re: [PATCH RFC] serio HIL MLC: don't deref null, don't leak and return proper error

[Helge Deller <deller@gmx.de>]

On 11/09/2010 07:35 AM, Dmitry Torokhov wrote:
> On Sun, Nov 07, 2010 at 08:36:33PM +0100, Jesper Juhl wrote:
>> Hi,
>>
>> While reviewing various users of kernel memory allocation functions I came
>> across drivers/input/serio/hil_mlc.c::hil_mlc_register() and noticed that
>>   - it calls kzalloc() buf fails to check for a NULL return before use.
>>   - it makes several allocations and if one fails it doesn't free the
>>     previous ones.
>>   - It doesn't return -ENOMEM in the failed memory allocation case (it just
>>     crashes).
>> This patch corrects all of the above and also reworks the only caller of
>> this function that I could find
>> (drivers/input/serio/hp_sdc_mlc.c::hp_sdc_mlc_out()) so that it now checks
>> the return value of hil_mlc_register() and properly propagate it on
>> failure and I also restructured the code to remove some labels and goto's
>> to make it, IMHO nicer to read.
>>
>> I have no hardware to test, so please review carefully and let me know if
>> I've done something completely stupid. Please don't merge this RFC patch
>> unless at least one or more people who know this code and can actually
>> test it have ACK'ed it.
> I think Helge Deller (CCed) used to have access to such hardware...

Yes, and I tested the patch successfully.

Tested-by: Helge Deller <deller@gmx.de>
Acked-by: Helge Deller <deller@gmx.de>


>> Signed-off-by: Jesper Juhl<jj@chaosbits.net>
>> ---
>>   hil_mlc.c    |    5 +++++
>>   hp_sdc_mlc.c |   18 +++++++++---------
>>   2 files changed, 14 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/input/serio/hil_mlc.c b/drivers/input/serio/hil_mlc.c
>> index e5624d8..bfd3865 100644
>> --- a/drivers/input/serio/hil_mlc.c
>> +++ b/drivers/input/serio/hil_mlc.c
>> @@ -932,6 +932,11 @@ int hil_mlc_register(hil_mlc *mlc)
>>   		hil_mlc_copy_di_scratch(mlc, i);
>>   		mlc_serio = kzalloc(sizeof(*mlc_serio), GFP_KERNEL);
>>   		mlc->serio[i] = mlc_serio;
>> +		if (!mlc->serio[i]) {
>> +			for (; i>= 0; i--)
>> +				kfree(mlc->serio[i]);
>> +			return -ENOMEM;
>> +		}
>>   		snprintf(mlc_serio->name, sizeof(mlc_serio->name)-1, "HIL_SERIO%d", i);
>>   		snprintf(mlc_serio->phys, sizeof(mlc_serio->phys)-1, "HIL%d", i);
>>   		mlc_serio->id			= hil_mlc_serio_id;
>> diff --git a/drivers/input/serio/hp_sdc_mlc.c b/drivers/input/serio/hp_sdc_mlc.c
>> index 7d2b820..d50f067 100644
>> --- a/drivers/input/serio/hp_sdc_mlc.c
>> +++ b/drivers/input/serio/hp_sdc_mlc.c
>> @@ -305,6 +305,7 @@ static void hp_sdc_mlc_out(hil_mlc *mlc)
>>   static int __init hp_sdc_mlc_init(void)
>>   {
>>   	hil_mlc *mlc =&hp_sdc_mlc;
>> +	int err;
>>
>>   #ifdef __mc68000__
>>   	if (!MACH_IS_HP300)
>> @@ -323,22 +324,21 @@ static int __init hp_sdc_mlc_init(void)
>>   	mlc->out =&hp_sdc_mlc_out;
>>   	mlc->priv =&hp_sdc_mlc_priv;
>>
>> -	if (hil_mlc_register(mlc)) {
>> +	err = hil_mlc_register(mlc);
>> +	if (err) {
>>   		printk(KERN_WARNING PREFIX "Failed to register MLC structure with hil_mlc\n");
>> -		goto err0;
>> +		return err;
>>   	}
>>
>>   	if (hp_sdc_request_hil_irq(&hp_sdc_mlc_isr)) {
>>   		printk(KERN_WARNING PREFIX "Request for raw HIL ISR hook denied\n");
>> -		goto err1;
>> +		if (hil_mlc_unregister(mlc))
>> +			printk(KERN_ERR PREFIX "Failed to unregister MLC structure with hil_mlc.\n"
>> +				"This is bad.  Could cause an oops.\n");
>> +		return -EBUSY;
>>   	}
>> +
>>   	return 0;
>> - err1:
>> -	if (hil_mlc_unregister(mlc))
>> -		printk(KERN_ERR PREFIX "Failed to unregister MLC structure with hil_mlc.\n"
>> -			"This is bad.  Could cause an oops.\n");
>> - err0:
>> -	return -EBUSY;
>>   }
>>
>>   static void __exit hp_sdc_mlc_exit(void)
>>
>>
>>