From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: oneukum@suse.com
Cc: syzbot <syzbot+9e04e2df4a32fb661daf@syzkaller.appspotmail.com>,
linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com,
andreyknvl@google.com, gregkh@linuxfoundation.org,
gustavoars@kernel.org, ingrassia@epigenesys.com,
lee.jones@linaro.org
Subject: [PATCH] USB: cdc-wdm: Fix use after free in service_outstanding_interrupt().
Date: Sun, 20 Dec 2020 00:25:53 +0900 [thread overview]
Message-ID: <620e2ee0-b9a3-dbda-a25b-a93e0ed03ec5@i-love.sakura.ne.jp> (raw)
In-Reply-To: <7a740f5a-65f9-b1d6-1224-4938d61b74a5@i-love.sakura.ne.jp>
syzbot is reporting UAF at usb_submit_urb() [1], for
service_outstanding_interrupt() is not checking WDM_DISCONNECTING
before calling usb_submit_urb(). Close the race by doing same checks
wdm_read() does upon retry.
Also, while wdm_read() checks WDM_DISCONNECTING with desc->rlock held,
service_interrupt_work() does not hold desc->rlock. Thus, it is possible
that usb_submit_urb() is called from service_outstanding_interrupt() from
service_interrupt_work() after WDM_DISCONNECTING was set and kill_urbs()
from wdm_disconnect() completed. Thus, move kill_urbs() in
wdm_disconnect() to after cancel_work_sync() (which makes sure that
service_interrupt_work() is no longer running) completed.
Although it seems to be safe to dereference desc->intf->dev in
service_outstanding_interrupt() even if WDM_DISCONNECTING was already set
because desc->rlock or cancel_work_sync() prevents wdm_disconnect() from
reaching list_del() before service_outstanding_interrupt() completes,
let's not emit error message if WDM_DISCONNECTING is set by
wdm_disconnect() while usb_submit_urb() is in progress.
[1] https://syzkaller.appspot.com/bug?extid=9e04e2df4a32fb661daf
Reported-by: syzbot <syzbot+9e04e2df4a32fb661daf@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
drivers/usb/class/cdc-wdm.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 02d0cfd23bb2..508b1c3f8b73 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -465,13 +465,23 @@ static int service_outstanding_interrupt(struct wdm_device *desc)
if (!desc->resp_count || !--desc->resp_count)
goto out;
+ if (test_bit(WDM_DISCONNECTING, &desc->flags)) {
+ rv = -ENODEV;
+ goto out;
+ }
+ if (test_bit(WDM_RESETTING, &desc->flags)) {
+ rv = -EIO;
+ goto out;
+ }
+
set_bit(WDM_RESPONDING, &desc->flags);
spin_unlock_irq(&desc->iuspin);
rv = usb_submit_urb(desc->response, GFP_KERNEL);
spin_lock_irq(&desc->iuspin);
if (rv) {
- dev_err(&desc->intf->dev,
- "usb_submit_urb failed with result %d\n", rv);
+ if (!test_bit(WDM_DISCONNECTING, &desc->flags))
+ dev_err(&desc->intf->dev,
+ "usb_submit_urb failed with result %d\n", rv);
/* make sure the next notification trigger a submit */
clear_bit(WDM_RESPONDING, &desc->flags);
@@ -1027,9 +1037,9 @@ static void wdm_disconnect(struct usb_interface *intf)
wake_up_all(&desc->wait);
mutex_lock(&desc->rlock);
mutex_lock(&desc->wlock);
- kill_urbs(desc);
cancel_work_sync(&desc->rxwork);
cancel_work_sync(&desc->service_outs_intr);
+ kill_urbs(desc);
mutex_unlock(&desc->wlock);
mutex_unlock(&desc->rlock);
--
2.25.1
next prev parent reply other threads:[~2020-12-19 15:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-07 12:19 KASAN: use-after-free Read in service_outstanding_interrupt syzbot
2020-12-18 3:21 ` syzbot
2020-12-18 14:03 ` Tetsuo Handa
2020-12-19 15:25 ` Tetsuo Handa [this message]
2020-12-28 14:44 ` [PATCH] USB: cdc-wdm: Fix use after free in service_outstanding_interrupt() Oliver Neukum
2021-01-04 16:28 ` KASAN: use-after-free Read in service_outstanding_interrupt Oliver Neukum
2021-01-04 16:44 ` syzbot
2021-01-05 4:50 ` 回复: " Zhang, Qiang
2021-01-05 10:51 ` Oliver Neukum
[not found] ` <20201218082113.1238-1-hdanton@sina.com>
2020-12-18 8:28 ` Greg KH
[not found] ` <20201218100134.1351-1-hdanton@sina.com>
2020-12-18 10:32 ` Greg KH
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