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From:   Pavel Skripkin <paskripkin@gmail.com>
To:     Larry.Finger@lwfinger.net, florian.c.schilhabel@googlemail.com,
        gregkh@linuxfoundation.org, zhansayabagdaulet@gmail.com,
        straube.linux@gmail.com
Cc:     linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org,
        Pavel Skripkin <paskripkin@gmail.com>,
        syzbot+5872a520e0ce0a7c7230@syzkaller.appspotmail.com,
        syzbot+cc699626e48a6ebaf295@syzkaller.appspotmail.com
Subject: [PATCH 2/2] staging: rtl8712: error handling refactoring
Date:   Wed, 21 Jul 2021 22:34:47 +0300
Message-Id: <d49ecc56e97c4df181d7bd4d240b031f315eacc3.1626895918.git.paskripkin@gmail.com>
In-Reply-To: <cover.1626895918.git.paskripkin@gmail.com>
References: <cover.1626895918.git.paskripkin@gmail.com>
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There was strange error handling logic in case of fw load failure. For
some reason fw loader callback was doing clean up stuff when fw is not
available. I don't see any reason behind doing this. Since this driver
doesn't have EEPROM firmware let's just disconnect it in case of fw load
failure. Doing clean up stuff in 2 different place which can run
concurently is not good idea and syzbot found 2 bugs related to this
strange approach.

So, in this pacth I deleted all clean up code from fw callback and made
a call to device_release_driver() under device_lock(parent) in case of fw
load failure. This approach is more generic and it defend driver from UAF
bugs, since all clean up code is moved to one place.

Fixes: e02a3b945816 ("staging: rtl8712: fix memory leak in rtl871x_load_fw_cb")
Fixes: 8c213fa59199 ("staging: r8712u: Use asynchronous firmware loading")
Reported-and-tested-by: syzbot+5872a520e0ce0a7c7230@syzkaller.appspotmail.com
Reported-and-tested-by: syzbot+cc699626e48a6ebaf295@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 drivers/staging/rtl8712/hal_init.c | 30 +++++++++++------
 drivers/staging/rtl8712/usb_intf.c | 52 +++++++++++++-----------------
 2 files changed, 43 insertions(+), 39 deletions(-)

diff --git a/drivers/staging/rtl8712/hal_init.c b/drivers/staging/rtl8712/hal_init.c
index 22974277afa0..4eff3fdecdb8 100644
--- a/drivers/staging/rtl8712/hal_init.c
+++ b/drivers/staging/rtl8712/hal_init.c
@@ -29,21 +29,31 @@
 #define FWBUFF_ALIGN_SZ 512
 #define MAX_DUMP_FWSZ (48 * 1024)
 
+static void rtl871x_load_fw_fail(struct _adapter *adapter)
+{
+	struct usb_device *udev = adapter->dvobjpriv.pusbdev;
+	struct device *dev = &udev->dev;
+	struct device *parent = dev->parent;
+
+	complete(&adapter->rtl8712_fw_ready);
+
+	dev_err(&udev->dev, "r8712u: Firmware request failed\n");
+
+	if (parent)
+		device_lock(parent);
+
+	device_release_driver(dev);
+
+	if (parent)
+		device_unlock(parent);
+}
+
 static void rtl871x_load_fw_cb(const struct firmware *firmware, void *context)
 {
 	struct _adapter *adapter = context;
 
 	if (!firmware) {
-		struct usb_device *udev = adapter->dvobjpriv.pusbdev;
-		struct usb_interface *usb_intf = adapter->pusb_intf;
-
-		dev_err(&udev->dev, "r8712u: Firmware request failed\n");
-		usb_put_dev(udev);
-		usb_set_intfdata(usb_intf, NULL);
-		r8712_free_drv_sw(adapter);
-		adapter->dvobj_deinit(adapter);
-		complete(&adapter->rtl8712_fw_ready);
-		free_netdev(adapter->pnetdev);
+		rtl871x_load_fw_fail(adapter);
 		return;
 	}
 	adapter->fw = firmware;
diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
index 643f21eb1128..505ebeb643dc 100644
--- a/drivers/staging/rtl8712/usb_intf.c
+++ b/drivers/staging/rtl8712/usb_intf.c
@@ -591,36 +591,30 @@ static void r871xu_dev_remove(struct usb_interface *pusb_intf)
 {
 	struct net_device *pnetdev = usb_get_intfdata(pusb_intf);
 	struct usb_device *udev = interface_to_usbdev(pusb_intf);
+	struct _adapter *padapter = netdev_priv(pnetdev);
+
+	/* never exit with a firmware callback pending */
+	wait_for_completion(&padapter->rtl8712_fw_ready);
+	usb_set_intfdata(pusb_intf, NULL);
+	release_firmware(padapter->fw);
+	if (drvpriv.drv_registered)
+		padapter->surprise_removed = true;
+	if (pnetdev->reg_state != NETREG_UNINITIALIZED)
+		unregister_netdev(pnetdev); /* will call netdev_close() */
+	r8712_flush_rwctrl_works(padapter);
+	r8712_flush_led_works(padapter);
+	udelay(1);
+	/* Stop driver mlme relation timer */
+	r8712_stop_drv_timers(padapter);
+	r871x_dev_unload(padapter);
+	r8712_free_drv_sw(padapter);
+	free_netdev(pnetdev);
+
+	/* decrease the reference count of the usb device structure
+	 * when disconnect
+	 */
+	usb_put_dev(udev);
 
-	if (pnetdev) {
-		struct _adapter *padapter = netdev_priv(pnetdev);
-
-		/* never exit with a firmware callback pending */
-		wait_for_completion(&padapter->rtl8712_fw_ready);
-		pnetdev = usb_get_intfdata(pusb_intf);
-		usb_set_intfdata(pusb_intf, NULL);
-		if (!pnetdev)
-			goto firmware_load_fail;
-		release_firmware(padapter->fw);
-		if (drvpriv.drv_registered)
-			padapter->surprise_removed = true;
-		if (pnetdev->reg_state != NETREG_UNINITIALIZED)
-			unregister_netdev(pnetdev); /* will call netdev_close() */
-		r8712_flush_rwctrl_works(padapter);
-		r8712_flush_led_works(padapter);
-		udelay(1);
-		/* Stop driver mlme relation timer */
-		r8712_stop_drv_timers(padapter);
-		r871x_dev_unload(padapter);
-		r8712_free_drv_sw(padapter);
-		free_netdev(pnetdev);
-
-		/* decrease the reference count of the usb device structure
-		 * when disconnect
-		 */
-		usb_put_dev(udev);
-	}
-firmware_load_fail:
 	/* If we didn't unplug usb dongle and remove/insert module, driver
 	 * fails on sitesurvey for the first time when device is up.
 	 * Reset usb port for sitesurvey fail issue.
-- 
2.32.0