linux-kernel - [PATCH] usb: gadget: pch

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Message-Id: <1573029503-18369-1-git-send-email-bianpan2016@163.com>
Date:   Wed,  6 Nov 2019 16:38:23 +0800
From:   Pan Bian <bianpan2016@....com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Colin Ian King <colin.king@...onical.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Chuhong Yuan <hslester96@...il.com>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pan Bian <bianpan2016@....com>
Subject: [PATCH] usb: gadget: pch_udc: fix use after free

The next field of the DMA descriptor is written after releasing the
descriptor, which may result in a use-after-free issue. Set the value of
the field before it is released to fix the bug.

Signed-off-by: Pan Bian <bianpan2016@....com>
---
 drivers/usb/gadget/udc/pch_udc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/pch_udc.c b/drivers/usb/gadget/udc/pch_udc.c
index 265dab2bbfac..c5b8ec908aab 100644
--- a/drivers/usb/gadget/udc/pch_udc.c
+++ b/drivers/usb/gadget/udc/pch_udc.c
@@ -1518,8 +1518,8 @@ 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;
-		dma_pool_free(dev->data_requests, td, addr);
 		td->next = 0x00;
+		dma_pool_free(dev->data_requests, td, addr);
 		addr = addr2;
 	}
 	req->chain_len = 1;
-- 
2.7.4