linux-kernel - Re: [PATCH] USB: whci-hcd: add more checks for dma mapping error

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Message-ID: <56F5C234.3070606@ispras.ru>
Date:	Sat, 26 Mar 2016 01:56:52 +0300
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	Vladimir Zapolskiy <vz@...ia.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org
Subject: Re: [PATCH] USB: whci-hcd: add more checks for dma mapping error

On 26.03.2016 01:03, Vladimir Zapolskiy wrote:
> On 25.03.2016 22:23, Alexey Khoroshilov wrote:
>> Fixing checks for dma mapping error in qset_fill_page_list(),
>> I have missed two similar problems in qset_add_urb_sg() and
>> in qset_add_urb_sg_linearize().
>>
>> Found by Linux Driver Verification project (linuxtesting.org).
>>
>> Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
>> ---
>>   drivers/usb/host/whci/qset.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/host/whci/qset.c b/drivers/usb/host/whci/qset.c
>> index 1a8e960d073b..a8e9b618e643 100644
>> --- a/drivers/usb/host/whci/qset.c
>> +++ b/drivers/usb/host/whci/qset.c
>> @@ -535,9 +535,11 @@ static int qset_add_urb_sg(struct whc *whc, struct whc_qset *qset, struct urb *u
>>   	list_for_each_entry(std, &qset->stds, list_node) {
>>   		if (std->ntds_remaining == -1) {
>>   			pl_len = std->num_pointers * sizeof(struct whc_page_list_entry);
>> -			std->ntds_remaining = ntds--;
>>   			std->dma_addr = dma_map_single(whc->wusbhc.dev, std->pl_virt,
>>   						       pl_len, DMA_TO_DEVICE);
>> +			if (dma_mapping_error(whc->wusbhc.dev, std->dma_addr))
>> +				return -EFAULT;
>
> Resources are leaked on error path:
> * std->pl_virt  -- most probably, at least it is freed on error path above,
> * dma mappings done in a loop before met error,
>

As far as I can see, it is not the case.
If qset_add_urb_sg() returns error code, the caller (qset_add_urb()) 
invokes qset_free_stds() that performs all resource deallocations.

As for the error path above, I consider it as a typical krealloc() 
pattern, since it does not frees memory allocated at previous iterations 
of the cycle.

Thank you,
Alexey