From: Alan Stern <stern@rowland.harvard.edu>
To: syzbot <syzbot+76629376e06e2c2ad626@syzkaller.appspotmail.com>
Cc: gregkh@linuxfoundation.org, hdanton@sina.com, johan@kernel.org,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
paskripkin@gmail.com, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] INFO: task hung in hub_port_init (2)
Date: Thu, 20 Jan 2022 12:28:42 -0500 [thread overview]
Message-ID: <YembypBPqEXg+YB+@rowland.harvard.edu> (raw)
In-Reply-To: <000000000000836a4805d5ff0b2b@google.com>
On Thu, Jan 20, 2022 at 12:11:10AM -0800, syzbot wrote:
> Hello,
>
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
>
> Reported-and-tested-by: syzbot+76629376e06e2c2ad626@syzkaller.appspotmail.com
>
> Tested on:
>
> commit: 6f59bc24 Add linux-next specific files for 20220118
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> kernel config: https://syzkaller.appspot.com/x/.config?x=94e8da4df9ab6319
> dashboard link: https://syzkaller.appspot.com/bug?extid=76629376e06e2c2ad626
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> patch: https://syzkaller.appspot.com/x/patch.diff?x=101ba7efb00000
>
> Note: testing is done by a robot and is best-effort only.
Attempted fix.
Alan Stern
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/ 6f59bc24
Index: usb-devel/drivers/usb/core/hcd.c
===================================================================
--- usb-devel.orig/drivers/usb/core/hcd.c
+++ usb-devel/drivers/usb/core/hcd.c
@@ -1563,6 +1563,12 @@ int usb_hcd_submit_urb (struct urb *urb,
urb->hcpriv = NULL;
INIT_LIST_HEAD(&urb->urb_list);
atomic_dec(&urb->use_count);
+ /*
+ * Order the write of urb->use_count above against the read of
+ * urb->reject below. Pairs with the memory barriers in
+ * usb_kill_urb() and usb_poison_urb().
+ */
+ smp_mb__after_atomic();
atomic_dec(&urb->dev->urbnum);
if (atomic_read(&urb->reject))
wake_up(&usb_kill_urb_queue);
@@ -1665,6 +1671,13 @@ static void __usb_hcd_giveback_urb(struc
usb_anchor_resume_wakeups(anchor);
atomic_dec(&urb->use_count);
+ /*
+ * Order the write of urb->use_count above against the read of
+ * urb->reject below. Pairs with the memory barriers in
+ * usb_kill_urb() and usb_poison_urb().
+ */
+ smp_mb__after_atomic();
+
if (unlikely(atomic_read(&urb->reject)))
wake_up(&usb_kill_urb_queue);
usb_put_urb(urb);
Index: usb-devel/drivers/usb/core/urb.c
===================================================================
--- usb-devel.orig/drivers/usb/core/urb.c
+++ usb-devel/drivers/usb/core/urb.c
@@ -715,6 +715,12 @@ void usb_kill_urb(struct urb *urb)
if (!(urb && urb->dev && urb->ep))
return;
atomic_inc(&urb->reject);
+ /*
+ * Order the write of urb->reject above against the read of
+ * urb->use_count below. Pairs with the barriers in
+ * __usb_hcd_giveback_urb() and usb_hcd_submit_urb().
+ */
+ smp_mb__after_atomic();
usb_hcd_unlink_urb(urb, -ENOENT);
wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
@@ -756,6 +762,12 @@ void usb_poison_urb(struct urb *urb)
if (!urb)
return;
atomic_inc(&urb->reject);
+ /*
+ * Order the write of urb->reject above against the read of
+ * urb->use_count below. Pairs with the barriers in
+ * __usb_hcd_giveback_urb() and usb_hcd_submit_urb().
+ */
+ smp_mb__after_atomic();
if (!urb->dev || !urb->ep)
return;
next prev parent reply other threads:[~2022-01-20 17:28 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220120080020.2619-1-hdanton@sina.com>
2022-01-20 8:11 ` [syzbot] INFO: task hung in hub_port_init (2) syzbot
2022-01-20 17:28 ` Alan Stern [this message]
2022-01-20 17:55 ` syzbot
[not found] <20220919111036.1016-1-hdanton@sina.com>
2022-09-19 11:37 ` syzbot
2021-11-16 2:47 syzbot
2022-01-19 20:16 ` syzbot
2022-09-19 1:54 ` syzbot
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