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Fri, 23 Oct 2026 00:31:40 -0700 (PDT) Received: from spiderman.taila3fd8c.ts.net ([202.112.47.77]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ea7af6eed2sm6766545ad.7.2026.10.23.00.31.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2026 00:31:40 -0700 (PDT) From: Li Ximo To: Greg Kroah-Hartman , Michal Simek Cc: linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Wang Haoran , Li Ximo Subject: [PATCH] usb: gadget: udc-xilinx: Fix wild pointer dereference on empty EP0 queue Date: Fri, 23 Oct 2026 15:31:31 +0800 Message-Id: <20261023073131.637062-1-lixicaicai@gmail.com> X-Mailer: git-send-email 2.25.1 X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Wang Haoran list_first_entry() does not return NULL when the list is empty; it returns the result of container_of() on the list head, i.e. a non-NULL wild pointer pointing into the enclosing struct xusb_ep rather than to a valid request. This was found by code audit. xudc_ep0_out() and xudc_ep0_in() are reached from the endpoint 0 interrupt handler xudc_ctrl_ep_handler() purely based on the hardware FIFO status bits, without checking whether ep0->queue actually holds a request. The queue can be empty at that point: the gadget driver's setup() callback may not queue a request for every control transfer stage, and xudc_done() removes the request once it completes, after which bus timing can raise another FIFO ready/free interrupt. The unconditional list_first_entry() then yields a wild pointer, and the subsequent accesses to req->usb_req.actual, req->usb_req.buf and req->usb_req.length read or write unrelated kernel memory, leading to memory corruption or a crash. On real hardware this is triggerable by an external USB host controlling the token timing. Note that the enqueue side __xudc_ep0_queue() already guards the same queue with list_empty(), which shows the queue can legitimately be empty; the dequeue side was simply missing the symmetric check. Switch both functions to list_first_entry_or_null() and return early when no request is queued, mirroring the existing list_empty() guard on the enqueue side. Reported-by: Wang Haoran Reported-by: Li Ximo Signed-off-by: Wang Haoran --- drivers/usb/gadget/udc/udc-xilinx.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/drivers/usb/gadget/udc/udc-xilinx.c b/drivers/usb/gadget/udc/udc-xilinx.c index bef06fe75..032d9f04f 100644 --- a/drivers/usb/gadget/udc/udc-xilinx.c +++ b/drivers/usb/gadget/udc/udc-xilinx.c @@ -1822,7 +1822,9 @@ static void xudc_ep0_out(struct xusb_udc *udc) unsigned int bytes_to_rx; void *buffer; - req = list_first_entry(&ep0->queue, struct xusb_req, queue); + req = list_first_entry_or_null(&ep0->queue, struct xusb_req, queue); + if (!req) + return; switch (udc->setupseqrx) { case STATUS_PHASE: @@ -1875,7 +1877,10 @@ static void xudc_ep0_in(struct xusb_udc *udc) u8 *ep0rambase; u8 test_mode = le16_to_cpu(udc->setup.wIndex) >> 8; - req = list_first_entry(&ep0->queue, struct xusb_req, queue); + req = list_first_entry_or_null(&ep0->queue, struct xusb_req, queue); + if (!req) + return; + bytes_to_tx = req->usb_req.length - req->usb_req.actual; switch (udc->setupseqtx) { -- 2.30.2