From: Greg KH <gregKH@linuxfoundation.org>
To: Oliver Neukum <oneukum@suse.com>
Cc: Himadri Pandya <himadrispandya@gmail.com>,
Alan Stern <stern@rowland.harvard.edu>,
linux-usb@vger.kernel.org
Subject: Re: usb_control_msg_send() and usb_control_msg_recv() are highly problematic
Date: Wed, 23 Sep 2020 13:07:24 +0200 [thread overview]
Message-ID: <20200923110724.GA3692555@kroah.com> (raw)
In-Reply-To: <1600858740.26851.16.camel@suse.com>
On Wed, Sep 23, 2020 at 12:59:00PM +0200, Oliver Neukum wrote:
> Hi,
>
> you probably do not want to hear this. I was out of comission
> for the last week weeks and I should have looked at this more closely.
>
> You may notice that usb_control_msg() for times immemorial has been
> using GFP_NOIO internally. This is because control messages are needed
> in a lot of contexts such as SCSI error handling and runtime PM
> that require GFP_NOIO. IIRC at that time we found ourselves unable to
> go through all those call chains, so we pulled the nuclear option
> and slapped a blanket GFP_NOIO on the function.
>
> Today I got a patch that outright deleted a memory allocation with
> GFP_NOIO, so I looked into this. We are making the same mistake
> we couldn't fix in the past.
> I am afraid the API has to be changed to include memory flags.
> And we should do this now while the damage is still within limits.
> I am preparing patches.
How about we always use GPF_NOIO for the calls? That should be fine and
make it easier, right?
thanks,
greg k-h
next prev parent reply other threads:[~2020-09-23 11:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-23 10:59 usb_control_msg_send() and usb_control_msg_recv() are highly problematic Oliver Neukum
2020-09-23 11:07 ` Greg KH [this message]
2020-09-23 11:28 ` Oliver Neukum
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