Re: [PATCH v2] usb: gadget: udc: remove pointer dereference after free

From: Gustavo A. R. Silva
Date: Tue Feb 14 2017 - 00:11:28 EST

Hi Michal,

Quoting Michal Nazarewicz <mina86@xxxxxxxxxx>:

On Sat, Feb 11 2017, Gustavo A. R. Silva wrote:
Remove pointer dereference after free and set pointer to NULL after free.

Addresses-Coverity-ID: 1091173
Signed-off-by: Gustavo A. R. Silva <garsilva@xxxxxxxxxxxxxx>

Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>

Changes in v2:
Move pointer dereference before pci_pool_free()
Set pointer to NULL after free

drivers/usb/gadget/udc/pch_udc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/pch_udc.c
index a97da64..73bb58f 100644
--- a/drivers/usb/gadget/udc/pch_udc.c
+++ b/drivers/usb/gadget/udc/pch_udc.c
@@ -1522,8 +1522,9 @@ static void pch_udc_free_dma_chain(struct
pch_udc_dev *dev,
/* do not free first desc., will be done by free for request */
td = phys_to_virt(addr);
addr2 = (dma_addr_t)td->next;
- pci_pool_free(dev->data_requests, td, addr);
td->next = 0x00;

Or just drop this. pci_pool_free doesnât care about contents of td.
Itâs just a void* for it.

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

This isnât necessary either. td will get overwritten on next iteration
and once weâre done itâs not used again.

addr = addr2;
req->chain_len = 1;

Thanks for your comments, I will send version 3 shortly.
Gustavo A. R. Silva