[PATCH] NVMe: Prevent possible NULL pointer dereference

[Keith Busch]

On Thu, 29 May 2014, J Freyensee wrote:
> On 05/28/2014 09:31 PM, Santosh Y wrote:
>> kmalloc() used by the nvme_alloc_iod() to allocate memory for 'iod'
>> can fail. So check the return value.
>> 
>> Signed-off-by: Santosh Y <santosh.sy at samsung.com>
>> 
>> diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
>> index cd8a8bc7..b089459 100644
>> --- a/drivers/block/nvme-core.c
>> +++ b/drivers/block/nvme-core.c
>> @@ -1488,7 +1488,11 @@ struct nvme_iod *nvme_map_user_pages(struct nvme_dev 
>> *dev, int write,
>>   		goto put_pages;
>>   	}
>> 
>> +	err = -ENOMEM;
>>   	iod = nvme_alloc_iod(count, length, GFP_KERNEL);
>> +	if (!iod)
>> +		goto put_pages;
>> +
>>   	sg = iod->sg;
>>   	sg_init_table(sg, count);
>>   	for (i = 0; i < count; i++) {
>> @@ -1501,7 +1505,6 @@ struct nvme_iod *nvme_map_user_pages(struct nvme_dev 
>> *dev, int write,
>>   	sg_mark_end(&sg[i - 1]);
>>   	iod->nents = count;
>> 
>> -	err = -ENOMEM;
>
> I am not that familiar with this nvme code yet, but should this statement be 
> left in?  It looks to me that this 'err = -ENOMEM;' assignment is for the 
> case if dma_map_sg() statement below it fails.

This is not being removed in the patch. It's just moved up higher in
the function.