From: Oliver Neukum <oneukum@suse.com>
To: Himadri Pandya <himadrispandya@gmail.com>,
gregKH@linuxfoundation.org,
Alan Stern <stern@rowland.harvard.edu>
Cc: linux-usb@vger.kernel.org
Subject: usb_control_msg_send() and usb_control_msg_recv() are highly problematic
Date: Wed, 23 Sep 2020 12:59:00 +0200 [thread overview]
Message-ID: <1600858740.26851.16.camel@suse.com> (raw)
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.
Regards
Oliver
next reply other threads:[~2020-09-23 10:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-23 10:59 Oliver Neukum [this message]
2020-09-23 11:07 ` usb_control_msg_send() and usb_control_msg_recv() are highly problematic Greg KH
2020-09-23 11:28 ` Oliver Neukum
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