回复: KASAN: use-after-free Read in service_outstanding_interrupt

[Zhang, Qiang]

________________________________________
发件人: Oliver Neukum <oneukum@xxxxxxxx>
发送时间: 2021年1月5日 0:28
收件人: syzbot; andreyknvl@xxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; gustavoars@xxxxxxxxxx; ingrassia@xxxxxxxxxxxxxx; lee.jones@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx; penguin-kernel@xxxxxxxxxxxxxxxxxxx; syzkaller-bugs@xxxxxxxxxxxxxxxx
主题: Re: KASAN: use-after-free Read in service_outstanding_interrupt

Am Donnerstag, den 17.12.2020, 19:21 -0800 schrieb syzbot:
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    5e60366d Merge tag 'fallthrough-fixes-clang-5.11-rc1' of g..
> 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=12c5b623500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5cea7506b7139727
> dashboard link: https://syzkaller.appspot.com/bug?extid=9e04e2df4a32fb661daf
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=175adf07500000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1672680f500000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: >syzbot+9e04e2df4a32fb661daf@xxxxxxxxxxxxxxxxxxxxxxxxx
>
>#syz test: https://github.com/google/kasan.git  5e60366d
>

 Hello Oliver 
 
 this use-after-free still exists，It can be seen from calltrace that it is 
 usb_device's object  has been released when disconnect,
 can add a reference count to usb_device's object to avoid this problem 
 
 diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 508b1c3f8b73..001cb93da6bf 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -106,6 +106,7 @@ struct wdm_device {
 
        struct list_head        device_list;
        int                     (*manage_power)(struct usb_interface *, int);
+       struct usb_device       *usb_dev;
 };
 
 static struct usb_driver wdm_driver;
@@ -338,6 +339,7 @@ static void free_urbs(struct wdm_device *desc)
 
 static void cleanup(struct wdm_device *desc)
 {
+       usb_put_dev(desc->usb_dev);
        kfree(desc->sbuf);
        kfree(desc->inbuf);
        kfree(desc->orq);
@@ -855,6 +857,7 @@ static int wdm_create(struct usb_interface *intf, struct usb_endpoint_descripto
r
        desc->intf = intf;
        INIT_WORK(&desc->rxwork, wdm_rxwork);
        INIT_WORK(&desc->service_outs_intr, service_interrupt_work);
+       desc->usb_dev = usb_get_dev(interface_to_usbdev(intf));
 
        rv = -EINVAL;
        if (!usb_endpoint_is_int_in(ep))




>From f51e3c5a202f3abc805edd64b21a68d29dd9d60e Mon Sep 17 >00:00:00 2001
>From: Oliver Neukum <oneukum@xxxxxxxx>
>Date: Mon, 4 Jan 2021 17:26:33 +0100
>Subject: [PATCH] cdc-wdm: poison URBs upon disconnect
>
>We have a chicken and egg issue between interrupt and work.
>This should break the cycle.
>
>Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
>---
>drivers/usb/class/cdc-wdm.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc->wdm.c
>index 02d0cfd23bb2..14eddda35280 100644
>--- a/drivers/usb/class/cdc-wdm.c
>+++ b/drivers/usb/class/cdc-wdm.c
>@@ -324,9 +324,9 @@ static void wdm_int_callback(struct urb *urb)
>static void kill_urbs(struct wdm_device *desc)
> {
>       /* the order here is essential */
>-       usb_kill_urb(desc->command);
>-       usb_kill_urb(desc->validity);
>-       usb_kill_urb(desc->response);
>+       usb_poison_urb(desc->command);
>+       usb_poison_urb(desc->validity);
>+       usb_poison_urb(desc->response);
> }
>
> static void free_urbs(struct wdm_device *desc)
>--
>2.26.2