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

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Message-Id: <20170328122850.18819-1-colin.king@canonical.com>
Date:   Tue, 28 Mar 2017 13:28:50 +0100
From:   Colin King <colin.king@...onical.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Michal Nazarewicz <mina86@...a86.com>,
        "Gustavo A . R . Silva" <garsilva@...eddedor.com>,
        Iago Abal <mail@...oabal.eu>,
        Romain Perier <romain.perier@...labora.com>,
        linux-usb@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] usb: gadget: pch_udc: don't update td->next after it has been released to the pool

From: Colin Ian King <colin.king@...onical.com>

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@...onical.com>
---
 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;
 		addr = addr2;
 	}
 	req->chain_len = 1;
-- 
2.11.0