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

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Message-ID: <0c06bad2c5454514ea6105de030374348abd7408.1486867169.git.garsilva@embeddedor.com>
Date:   Mon, 13 Feb 2017 09:40:02 -0600
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     balbi@...nel.org, gregkh@...uxfoundation.org, bhelgaas@...gle.com,
        mina86@...a86.com, heikki.krogerus@...ux.intel.com
Cc:     linux-geode@...ts.infradead.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] usb: gadget: udc: avoid use of freed pointer

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

Addresses-Coverity-ID: 1091172
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.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