linux-kernel - [PATCH 1/1] usb: cdns3 fix use-after-free at workaround 2

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Message-Id: <20220608190430.2814358-1-Frank.Li@nxp.com>
Date:   Wed,  8 Jun 2022 14:04:30 -0500
From:   Frank Li <Frank.Li@....com>
To:     peter.chen@...nel.org, pawell@...ence.com, rogerq@...nel.org,
        a-govindraju@...com, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        lznuaa@...il.com
Subject: [PATCH 1/1] usb: cdns3 fix use-after-free at workaround 2

BUG: KFENCE: use-after-free read in __list_del_entry_valid+0x10/0xac

cdns3_wa2_remove_old_request()
{
	...
	kfree(priv_req->request.buf);
	cdns3_gadget_ep_free_request(&priv_ep->endpoint, &priv_req->request);
	list_del_init(&priv_req->list);
	^^^ use after free
	...
}

cdns3_gadget_ep_free_request() free the space pointed by priv_req,
but priv_req is used in the following list_del_init().

This patch move list_del_init() before cdns3_gadget_ep_free_request().

Signed-off-by: Frank Li <Frank.Li@....com>
Signed-off-by: Faqiang Zhu <faqiang.zhu@....com>
---
 drivers/usb/cdns3/cdns3-gadget.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
index 5c15c48952a61..29662c8ac0242 100644
--- a/drivers/usb/cdns3/cdns3-gadget.c
+++ b/drivers/usb/cdns3/cdns3-gadget.c
@@ -625,9 +625,9 @@ static void cdns3_wa2_remove_old_request(struct cdns3_endpoint *priv_ep)
 		trace_cdns3_wa2(priv_ep, "removes eldest request");
 
 		kfree(priv_req->request.buf);
+		list_del_init(&priv_req->list);
 		cdns3_gadget_ep_free_request(&priv_ep->endpoint,
 					     &priv_req->request);
-		list_del_init(&priv_req->list);
 		--priv_ep->wa2_counter;
 
 		if (!chain)
-- 
2.35.1