From: Oliver Neukum <oneukum@suse.com>
To: Gui-Dong Han <hanguidong02@gmail.com>, Oliver Neukum <oneukum@suse.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
robert.hodaszi@digi.com, kees@kernel.org,
linux-usb@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Jia-Ju Bai <baijiaju1990@gmail.com>
Subject: Re: [BUG] usb: cdc-wdm: Missing barriers in ad-hoc lockless buffer
Date: Thu, 5 Mar 2026 13:44:31 +0100 [thread overview]
Message-ID: <678e1fc6-356d-426a-aec0-f0bf46c7d3af@suse.com> (raw)
In-Reply-To: <CALbr=Lb6Vir4+O-=8-iL7M8=Gqgm=VUp6s+XGVC75QixFaSmOA@mail.gmail.com>
On 05.03.26 13:28, Gui-Dong Han wrote:
> Specifically, wdm_read() accesses ->length and then ->flags, often
> without holding ->iuspin. Similarly, wdm_in_callback() involves
> multiple accesses to both.
>
> I am indeed nervous about this pattern. Without barriers, changes to
> these associated fields made on one CPU might be observed in a
> completely different order on another CPU.
OK, I rechecked. And indeed it seems to me like setting WDM_OVERFLOW
and WDM_READ could be reordered with respect to each other in
wdm_in_callback() and that must not happen.
What do you think?
Regards
Oliver
next prev parent reply other threads:[~2026-03-05 12:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-04 8:41 Gui-Dong Han
2026-03-04 9:15 ` Greg KH
2026-03-05 11:35 ` Oliver Neukum
2026-03-05 12:28 ` Gui-Dong Han
2026-03-05 12:44 ` Oliver Neukum [this message]
2026-03-05 13:26 ` Gui-Dong Han
2026-03-06 9:25 ` Oliver Neukum
2026-03-06 10:36 ` Gui-Dong Han
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