Re: [PATCH] usb: gadget: pch_udc: don't update td->next after it has been released to the pool

[Colin Ian King]

On 28/03/17 13:51, Felipe Balbi wrote:
> 
> Hi,
> 
> Colin King <colin.king@xxxxxxxxxxxxx> writes:
>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>
>> Writing to td->next should be avoided after td has been freed using
>> dma_pool_free. The intent was to nullify the next pointer, but this
>> is potentially dangerous once it is back in the pool. Remove it.
>>
>> Detected by CoverityScan, CID#1091173 ("Write tp pointer after free")
>>
>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>> ---
>>  drivers/usb/gadget/udc/pch_udc.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/usb/gadget/udc/pch_udc.c b/drivers/usb/gadget/udc/pch_udc.c
>> index 84dcbcd756f0..08bbe2c24134 100644
>> --- a/drivers/usb/gadget/udc/pch_udc.c
>> +++ b/drivers/usb/gadget/udc/pch_udc.c
>> @@ -1523,7 +1523,6 @@ static void pch_udc_free_dma_chain(struct pch_udc_dev *dev,
>>  		td = phys_to_virt(addr);
>>  		addr2 = (dma_addr_t)td->next;
>>  		dma_pool_free(dev->data_requests, td, addr);
>> -		td->next = 0x00;
> 
> I already have a patch for this, thanks

Ah, I somehow overlooked that. Good to see it is fixed.

Colin

> 
> 1f459262b0e1649a1e5ad12fa4c66eb76c2220ce
> Author:     Gustavo A. R. Silva <garsilva@xxxxxxxxxxxxxx>
> AuthorDate: Fri Mar 10 15:39:32 2017 -0600
> Commit:     Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> CommitDate: Wed Mar 22 11:21:10 2017 +0200
> 
> usb: gadget: udc: remove pointer dereference after free
> 
> Remove pointer dereference after free.
> 
> Addresses-Coverity-ID: 1091173
> Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
> Signed-off-by: Gustavo A. R. Silva <garsilva@xxxxxxxxxxxxxx>
> Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> 
> 1 file changed, 1 deletion(-)
> drivers/usb/gadget/udc/pch_udc.c | 1 -
> 
> modified   drivers/usb/gadget/udc/pch_udc.c
> @@ -1523,7 +1523,6 @@ static void pch_udc_free_dma_chain(struct pch_udc_dev *dev,
>  		td = phys_to_virt(addr);
>  		addr2 = (dma_addr_t)td->next;
>  		pci_pool_free(dev->data_requests, td, addr);
> -		td->next = 0x00;
>  		addr = addr2;
>  	}
>  	req->chain_len = 1;
>