Re: [syzbot] KASAN: use-after-free Read in rtl8712_dl_fw

[Pavel Skripkin <paskripkin@gmail.com>]

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On 10/19/21 18:29, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    8ef1e58783b9 usb: typec: STUSB160X should select REGMAP_I2C
> git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
> console output: https://syzkaller.appspot.com/x/log.txt?x=1106dcfb300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c27d285bdb7457e2
> dashboard link: https://syzkaller.appspot.com/bug?extid=c55162be492189fb4f51
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12725770b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1168c158b00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c55162be492189fb4f51@syzkaller.appspotmail.com
> 

Ok, this driver can't be fixed.... Let's try unregister netdev before 
doing clean up stuff to not race with ->ndo_open()

#syz test: 
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing





With regards,
Pavel Skripkin

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diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
index 505ebeb643dc..cae04272deff 100644
--- a/drivers/staging/rtl8712/usb_intf.c
+++ b/drivers/staging/rtl8712/usb_intf.c
@@ -595,12 +595,12 @@ static void r871xu_dev_remove(struct usb_interface *pusb_intf)
 
 	/* never exit with a firmware callback pending */
 	wait_for_completion(&padapter->rtl8712_fw_ready);
+	if (pnetdev->reg_state != NETREG_UNINITIALIZED)
+		unregister_netdev(pnetdev); /* will call netdev_close() */
 	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);