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([163.239.22.29]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8b35aa98162sm468581b3a.56.2026.11.06.01.53.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2026 01:53:07 -0800 (PST) From: hyunjungg To: David Heidelberg Cc: oe-linux-nfc@lists.linux.dev, linux-kernel@vger.kernel.org, Hyunjung Ko Subject: [PATCH] nfc: port100: drain cmd_complete_work before freeing the device on disconnect Date: Fri, 6 Nov 2026 18:52:57 +0900 Message-ID: <20261106095257.2407520-1-hj351016@gmail.com> X-Mailer: git-send-email 2.43.0 X-Mailing-List: linux-kernel@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: Hyunjung Ko port100_disconnect() tears the device down in an order that lets cmd_complete_work run against freed memory: nfc_digital_unregister_device(dev->nfc_digital_dev); nfc_digital_free_device(dev->nfc_digital_dev); /* ddev freed */ usb_kill_urb(dev->in_urb); /* -> schedule_work() */ usb_kill_urb(dev->out_urb); usb_free_urb(dev->in_urb); usb_free_urb(dev->out_urb); kfree(dev->cmd); /* cmd freed */ nfc_digital_unregister_device() does not abort a transport command that is already in flight, so an IN URB can still be pending here. The URB completion handlers port100_recv_response() / port100_recv_ack() schedule cmd_complete_work whenever the IN URB completes with an error status, including the -ECONNRESET that usb_kill_urb(dev->in_urb) produces synchronously for the in-flight command. The work handler port100_wq_cmd_complete() then runs port100_send_async_complete(): static void port100_send_async_complete(struct port100 *dev) { struct port100_cmd *cmd = dev->cmd; int status = cmd->status; /* UAF read */ ... cmd->complete_cb(dev->nfc_digital_dev, ...); /* freed ddev */ ... kfree(cmd); /* double free */ } Nothing drains the work, so a command in flight at disconnect leaves cmd_complete_work queued (or running) and it dereferences dev->cmd (freed by kfree(dev->cmd)), dev->nfc_digital_dev (freed by nfc_digital_free_device()) and ultimately dev itself (devres-freed after disconnect returns) -> a use-after-free plus double-free. Kill the URBs and cancel_work_sync() the work *before* nfc_digital_free_device(), so the completion that usb_kill_urb() forces cannot re-queue the work and the handler cannot run (or is waited out) while dev->nfc_digital_dev and dev are still valid. Placing the drain after nfc_digital_free_device() would be insufficient: on SMP/PREEMPT a worker that already started executing would be waited on by cancel_work_sync() while dereferencing the already-freed ddev. Found by code review and reproduced on 7.3-rc3 with KASAN and DEBUG_OBJECTS, using dummy_hcd + raw_gadget to emulate the device and race an in-flight command against USB disconnect: debugobjects reports a free-active work_struct for port100_wq_cmd_complete, freed from devres_release_all() via kfree() while still queued. Signed-off-by: Hyunjung Ko --- drivers/nfc/port100.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/nfc/port100.c b/drivers/nfc/port100.c --- a/drivers/nfc/port100.c +++ b/drivers/nfc/port100.c @@ -1619,13 +1619,15 @@ static void port100_disconnect(struct usb_interface *interface) dev = usb_get_intfdata(interface); usb_set_intfdata(interface, NULL); nfc_digital_unregister_device(dev->nfc_digital_dev); - nfc_digital_free_device(dev->nfc_digital_dev); usb_kill_urb(dev->in_urb); usb_kill_urb(dev->out_urb); + cancel_work_sync(&dev->cmd_complete_work); + + nfc_digital_free_device(dev->nfc_digital_dev); usb_free_urb(dev->in_urb); usb_free_urb(dev->out_urb); kfree(dev->cmd);