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

Gustavo A. R. Silva
2017-02-13T16:07:03Z

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

Addresses-Coverity-ID: 1091172
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
---
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;
+ 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;
+ pci_pool_free(dev->data_requests, td, addr);
+ td = NULL;
+ addr = addr_aux;
}

return ret_val;
--
2.5.0