Re: [stable] [PATCH] [SCSI] libiscsi: fix iscsi pool error path

[Mike Christie <michaelc@cs.wisc.edu>]

Jean Delvare wrote:
> Hi Chris,
> 
> Le lundi 30 mars 2009, Chris Wright a écrit :
>> * Jean Delvare (jdelvare@suse.de) wrote:
>>> --- linux-2.6.29-rc5.orig/drivers/scsi/libiscsi.c	2009-01-29 08:27:19.000000000 +0100
>>> +++ linux-2.6.29-rc5/drivers/scsi/libiscsi.c	2009-02-16 21:19:14.000000000 +0100
>>> @@ -1944,7 +1944,7 @@ iscsi_pool_init(struct iscsi_pool *q, in
>>>  		num_arrays++;
>>>  	q->pool = kzalloc(num_arrays * max * sizeof(void*), GFP_KERNEL);
>>>  	if (q->pool == NULL)
>>> -		goto enomem;
>>> +		return -ENOMEM;
>>>  
>>>  	q->queue = kfifo_init((void*)q->pool, max * sizeof(void*),
>>>  			      GFP_KERNEL, NULL);
>>> @@ -1979,8 +1979,7 @@ void iscsi_pool_free(struct iscsi_pool *
>>>  
>>>  	for (i = 0; i < q->max; i++)
>>>  		kfree(q->pool[i]);
>>> -	if (q->pool)
>>> -		kfree(q->pool);
>>> +	kfree(q->pool);
>>>  	kfree(q->queue);
>> AFAICT, This is still broken.
>>
>> thanks,
>> -chris
>> --
>>
>> Subject: [PATCH] libiscsi: fix error path on iscsi_pool_init
>>
>> From: Chris Wright <chrisw@sous-sol.org>
>>
>> I'm not all that keen on kfifo_init returning ERR_PTR, but...
> 
> Ah, I had not noticed this. Good catch!
> 

Yeah, thanks Chris.


>> q->queue could be ERR_PTR(-ENOMEM) which will break unwinding
>> on error.  Make iscsi_pool_free more defensive.
>>
>> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
>> ---
>> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
>> index dfaa8ad..2f4df53 100644
>> --- a/drivers/scsi/libiscsi.c
>> +++ b/drivers/scsi/libiscsi.c
>> @@ -1995,7 +1995,7 @@ iscsi_pool_init(struct iscsi_pool *q, int max, void ***items, int item_size)
>>  		num_arrays++;
>>  	q->pool = kzalloc(num_arrays * max * sizeof(void*), GFP_KERNEL);
>>  	if (q->pool == NULL)
>> -		return -ENOMEM;
>> +		goto enomem;
>>  
>>  	q->queue = kfifo_init((void*)q->pool, max * sizeof(void*),
>>  			      GFP_KERNEL, NULL);
>> @@ -2028,10 +2028,13 @@ void iscsi_pool_free(struct iscsi_pool *q)
>>  {
>>  	int i;
>>  
>> -	for (i = 0; i < q->max; i++)
>> -		kfree(q->pool[i]);
>> -	kfree(q->pool);
>> -	kfree(q->queue);
>> +	if (q->pool) {
>> +		for (i = 0; i < q->max; i++)
>> +			kfree(q->pool[i]);
>> +		kfree(q->pool);
>> +		if (!IS_ERR(q->queue))
>> +			kfree(q->queue);
>> +	}
>>  }
>>  EXPORT_SYMBOL_GPL(iscsi_pool_free);
> 
> Making the freeing of q->queue dependent on q->pool being set looks
> really weird (although it is correct at the moment. But this seems
> to be fixable in a much simpler way:
> 
> ---
>  drivers/scsi/libiscsi.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> --- linux-2.6.30-rc0.orig/drivers/scsi/libiscsi.c	2009-03-30 09:27:48.000000000 +0200
> +++ linux-2.6.30-rc0/drivers/scsi/libiscsi.c	2009-03-30 21:15:13.000000000 +0200
> @@ -1999,8 +1999,10 @@ iscsi_pool_init(struct iscsi_pool *q, in
>  
>  	q->queue = kfifo_init((void*)q->pool, max * sizeof(void*),
>  			      GFP_KERNEL, NULL);
> -	if (q->queue == ERR_PTR(-ENOMEM))
> +	if (q->queue == ERR_PTR(-ENOMEM)) {
> +		q->queue = NULL;
>  		goto enomem;
> +	}
>  
>  	for (i = 0; i < max; i++) {
>  		q->pool[i] = kzalloc(item_size, GFP_KERNEL);
> 
> With the benefit that only the error case is slowed down. In both
> cases we have a problem if q->queue contains an error value but it's
> not -ENOMEM. Apparently this can't happen today, but it doesn't feel
> right to assume this will always be true. Maybe it's the right time
> to fix this as well.
> 

Yeah I agree. I will just modify the patch to check for IS_ERR(q->queue) 
in there.

I will do a quick sanity test on it here then pass it on to James with 
some other stuff for 2.6.30.

Thanks.
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