Re: [PATCH 1/2] usb: gadget: udc: avoid use of freed pointer

[Gustavo A. R. Silva]

Hi Michal,

Quoting Michal Nazarewicz :


On Mon, Feb 13 2017, Gustavo A. R. Silva wrote:

Rewrite udc_free_dma_chain() function to avoid use of pointer after free.

Addresses-Coverity-ID: 1091172
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Gustavo A. R. Silva 


Acked-by: Michal Nazarewicz 


---
 drivers/usb/gadget/udc/amd5536udc.c | 20 +++-
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/gadget/udc/amd5536udc.c  
b/drivers/usb/gadget/udc/amd5536udc.c

index ea03ca7..ded97a3 100644
--- a/drivers/usb/gadget/udc/amd5536udc.c
+++ b/drivers/usb/gadget/udc/amd5536udc.c
@@ -611,21 +611,23 @@ udc_alloc_request(struct usb_ep *usbep, gfp_t gfp)
 static int udc_free_dma_chain(struct udc *dev, struct udc_request *req)
 {
int ret_val = 0;
-   struct udc_data_dma *td;
-   struct udc_data_dma *td_last = NULL;
+   struct udc_data_dma *td = req->td_data;
unsigned int i;

+   dma_addr_t addr_aux = 0x00;


Perhaps call it ‘addr_next’ or ‘next’?


+   dma_addr_t addr = (dma_addr_t)td->next;
+   td->next = 0x00;
+
DBG(dev, "free chain req = %p\n", req);

/* do not free first desc., will be done by free for request */
-   td_last = req->td_data;
-   td = phys_to_virt(td_last->next);
-
for (i = 1; i < req->chain_len; i++) {
-   pci_pool_free(dev->data_requests, td,
- (dma_addr_t)td_last->next);
-   td_last = td;
-   td = phys_to_virt(td_last->next);
+   td = phys_to_virt(addr);
+   addr_aux = (dma_addr_t)td->next;
+   td->next = 0x00;


This is unnecessary.


+   pci_pool_free(dev->data_requests, td, addr);
+   td = NULL;


Ditto.


+   addr = addr_aux;
}

return ret_val;
--
2.5.0





Thanks for your comments, I will send version 2 shortly.
--
Gustavo A. R. Silva

Re: [PATCH 1/2] usb: gadget: udc: avoid use of freed pointer

[Michal Nazarewicz]

On Mon, Feb 13 2017, Gustavo A. R. Silva wrote:
> Rewrite udc_free_dma_chain() function to avoid use of pointer after free.
>
> Addresses-Coverity-ID: 1091172
> Reviewed-by: Greg Kroah-Hartman 
> Signed-off-by: Gustavo A. R. Silva 

Acked-by: Michal Nazarewicz 

> ---
>  drivers/usb/gadget/udc/amd5536udc.c | 20 +++-
>  1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/amd5536udc.c 
> b/drivers/usb/gadget/udc/amd5536udc.c
> index ea03ca7..ded97a3 100644
> --- a/drivers/usb/gadget/udc/amd5536udc.c
> +++ b/drivers/usb/gadget/udc/amd5536udc.c
> @@ -611,21 +611,23 @@ udc_alloc_request(struct usb_ep *usbep, gfp_t gfp)
>  static int udc_free_dma_chain(struct udc *dev, struct udc_request *req)
>  {
>   int ret_val = 0;
> - struct udc_data_dma *td;
> - struct udc_data_dma *td_last = NULL;
> + struct udc_data_dma *td = req->td_data;
>   unsigned int i;
>  
> + dma_addr_t addr_aux = 0x00;

Perhaps call it ‘addr_next’ or ‘next’?

> + dma_addr_t addr = (dma_addr_t)td->next;
> + td->next = 0x00;
> +
>   DBG(dev, "free chain req = %p\n", req);
>  
>   /* do not free first desc., will be done by free for request */
> - td_last = req->td_data;
> - td = phys_to_virt(td_last->next);
> -
>   for (i = 1; i < req->chain_len; i++) {
> - pci_pool_free(dev->data_requests, td,
> -   (dma_addr_t)td_last->next);
> - td_last = td;
> - td = phys_to_virt(td_last->next);
> + td = phys_to_virt(addr);
> + addr_aux = (dma_addr_t)td->next;
> + td->next = 0x00;

This is unnecessary.

> + pci_pool_free(dev->data_requests, td, addr);
> + td = NULL;

Ditto.

> + addr = addr_aux;
>   }
>  
>   return ret_val;
> -- 
> 2.5.0
>

-- 
Best regards
ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ
«If at first you don’t succeed, give up skydiving»