Re: WARNING in r871xu_dev_remove

[Oliver Neukum <oneukum@suse.com>]

Am Donnerstag, den 22.08.2019, 07:28 -0700 schrieb syzbot:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    eea39f24 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=163ae012600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d0c62209eedfd54e
> dashboard link: https://syzkaller.appspot.com/bug?extid=80899a8a8efe8968cde7
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1739cb0e600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154fcc2e600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+80899a8a8efe8968cde7@syzkaller.appspotmail.com

#syz test: https://github.com/google/kasan.git eea39f24

From 4f21b5aabc448719aa612b9359d90a178cb485d8 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Thu, 22 Aug 2019 16:37:33 +0200
Subject: [PATCH] rtl8712: fix race between firmware failing to load and
 disconnect

We have to wait for the attempt to load the firmware to finish
before we evaluate the result.

Reported-by: syzbot+80899a8a8efe8968cde7@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/staging/rtl8712/hal_init.c | 3 ++-
 drivers/staging/rtl8712/usb_intf.c | 8 ++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/rtl8712/hal_init.c b/drivers/staging/rtl8712/hal_init.c
index 40145c0338e4..42c0a3c947f1 100644
--- a/drivers/staging/rtl8712/hal_init.c
+++ b/drivers/staging/rtl8712/hal_init.c
@@ -33,7 +33,6 @@ static void rtl871x_load_fw_cb(const struct firmware *firmware, void *context)
 {
 	struct _adapter *adapter = context;
 
-	complete(&adapter->rtl8712_fw_ready);
 	if (!firmware) {
 		struct usb_device *udev = adapter->dvobjpriv.pusbdev;
 		struct usb_interface *usb_intf = adapter->pusb_intf;
@@ -41,11 +40,13 @@ static void rtl871x_load_fw_cb(const struct firmware *firmware, void *context)
 		dev_err(&udev->dev, "r8712u: Firmware request failed\n");
 		usb_put_dev(udev);
 		usb_set_intfdata(usb_intf, NULL);
+		complete(&adapter->rtl8712_fw_ready);
 		return;
 	}
 	adapter->fw = firmware;
 	/* firmware available - start netdev */
 	register_netdev(adapter->pnetdev);
+	complete(&adapter->rtl8712_fw_ready);
 }
 
 static const char firmware_file[] = "rtlwifi/rtl8712u.bin";
diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
index d0daae0b8299..8d7b57073592 100644
--- a/drivers/staging/rtl8712/usb_intf.c
+++ b/drivers/staging/rtl8712/usb_intf.c
@@ -595,10 +595,13 @@ static void r871xu_dev_remove(struct usb_interface *pusb_intf)
 	if (pnetdev) {
 		struct _adapter *padapter = netdev_priv(pnetdev);
 
-		usb_set_intfdata(pusb_intf, NULL);
-		release_firmware(padapter->fw);
 		/* 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 raced_with_firmware_failure;
+		release_firmware(padapter->fw);
 		if (drvpriv.drv_registered)
 			padapter->surprise_removed = true;
 		unregister_netdev(pnetdev); /* will call netdev_close() */
@@ -609,6 +612,7 @@ static void r871xu_dev_remove(struct usb_interface *pusb_intf)
 		r871x_dev_unload(padapter);
 		r8712_free_drv_sw(padapter);
 
+raced_with_firmware_failure:
 		/* decrease the reference count of the usb device structure
 		 * when disconnect
 		 */
-- 
2.16.4