[PATCH] ieee802154: atusb: fix use-after-free at disconnect

[PATCH] ieee802154: atusb: fix use-after-free at disconnect

[Johan Hovold]

The disconnect callback was accessing the hardware-descriptor private
data after having having freed it.

Fixes: 7490b008d123 ("ieee802154: add support for atusb transceiver")
Cc: stable <stable@vger.kernel.org>     # 4.2
Cc: Alexander Aring <alex.aring@gmail.com>
Reported-by: syzbot+f4509a9138a1472e7e80@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>
---

#syz test: https://github.com/google/kasan.git f0df5c1b

 drivers/net/ieee802154/atusb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ieee802154/atusb.c b/drivers/net/ieee802154/atusb.c
index ceddb424f887..0dd0ba915ab9 100644
--- a/drivers/net/ieee802154/atusb.c
+++ b/drivers/net/ieee802154/atusb.c
@@ -1137,10 +1137,11 @@ static void atusb_disconnect(struct usb_interface *interface)
 
 	ieee802154_unregister_hw(atusb->hw);
 
+	usb_put_dev(atusb->usb_dev);
+
 	ieee802154_free_hw(atusb->hw);
 
 	usb_set_intfdata(interface, NULL);
-	usb_put_dev(atusb->usb_dev);
 
 	pr_debug("%s done\n", __func__);
 }
-- 
2.23.0

Re: KASAN: use-after-free Read in atusb_disconnect

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger  
crash:

Reported-and-tested-by:  
syzbot+f4509a9138a1472e7e80@syzkaller.appspotmail.com

Tested on:

commit:         f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=f4509a9138a1472e7e80
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10f3ebb5600000

Note: testing is done by a robot and is best-effort only.

Re: [PATCH] ieee802154: atusb: fix use-after-free at disconnect

[Stefan Schmidt]

Hello.

On 19.09.19 14:12, Johan Hovold wrote:
> The disconnect callback was accessing the hardware-descriptor private
> data after having having freed it.
> 
> Fixes: 7490b008d123 ("ieee802154: add support for atusb transceiver")
> Cc: stable <stable@vger.kernel.org>     # 4.2
> Cc: Alexander Aring <alex.aring@gmail.com>
> Reported-by: syzbot+f4509a9138a1472e7e80@syzkaller.appspotmail.com
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
> 
> #syz test: https://github.com/google/kasan.git f0df5c1b
> 
>  drivers/net/ieee802154/atusb.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ieee802154/atusb.c b/drivers/net/ieee802154/atusb.c
> index ceddb424f887..0dd0ba915ab9 100644
> --- a/drivers/net/ieee802154/atusb.c
> +++ b/drivers/net/ieee802154/atusb.c
> @@ -1137,10 +1137,11 @@ static void atusb_disconnect(struct usb_interface *interface)
>  
>  	ieee802154_unregister_hw(atusb->hw);
>  
> +	usb_put_dev(atusb->usb_dev);
> +
>  	ieee802154_free_hw(atusb->hw);
>  
>  	usb_set_intfdata(interface, NULL);
> -	usb_put_dev(atusb->usb_dev);
>  
>  	pr_debug("%s done\n", __func__);
>  }
> 


This patch has been applied to the wpan tree and will be
part of the next pull request to net.

Thanks a lot for having a look at this!

regards
Stefan Schmidt