HID: intel-ish-hid: ipc: Fix potential use-after-free in work function

When a reset notify IPC message is received, the ISR schedules a work
function and passes the ISHTP device to it via a global pointer
ishtp_dev. If ish_probe() fails, the devm-managed device resources
including ishtp_dev are freed, but the work is not cancelled, causing a
use-after-free when the work function tries to access ishtp_dev. Use
devm_work_autocancel() instead, so that the work is automatically
cancelled if probe fails.
Signed-off-by: Reka Norman <rekanorman@chromium.org>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/intel-ish-hid/ipc/ipc.c

@@ -5,6 +5,7 @@
  * Copyright (c) 2014-2016, Intel Corporation.
  */
 
+#include <linux/devm-helpers.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/delay.h>
@@ -621,7 +622,6 @@ static void	recv_ipc(struct ishtp_device *dev, uint32_t doorbell_val)
 	case MNG_RESET_NOTIFY:
 		if (!ishtp_dev) {
 			ishtp_dev = dev;
-			INIT_WORK(&fw_reset_work, fw_reset_work_fn);
 		}
 		schedule_work(&fw_reset_work);
 		break;
@@ -940,6 +940,7 @@ struct ishtp_device *ish_dev_init(struct pci_dev *pdev)
 {
 	struct ishtp_device *dev;
 	int	i;
+	int	ret;
 
 	dev = devm_kzalloc(&pdev->dev,
 			   sizeof(struct ishtp_device) + sizeof(struct ish_hw),
@@ -975,6 +976,12 @@ struct ishtp_device *ish_dev_init(struct pci_dev *pdev)
 		list_add_tail(&tx_buf->link, &dev->wr_free_list);
 	}
 
+	ret = devm_work_autocancel(&pdev->dev, &fw_reset_work, fw_reset_work_fn);
+	if (ret) {
+		dev_err(dev->devc, "Failed to initialise FW reset work\n");
+		return NULL;
+	}
+
 	dev->ops = &ish_hw_ops;
 	dev->devc = &pdev->dev;
 	dev->mtu = IPC_PAYLOAD_SIZE - sizeof(struct ishtp_msg_hdr);