Re: [stable] locks: fix a potential use-after-free problem when wakeup a waiter

Ben Hutchings
2020-03-19T19:28:03Z

On Thu, 2020-03-19 at 07:37 +0100, Greg Kroah-Hartman wrote:
> On Wed, Mar 18, 2020 at 06:29:06PM -0400, Sasha Levin wrote:
> > On Wed, Mar 18, 2020 at 10:09:20PM +0000, Ben Hutchings wrote:
> > > This commit (included in 5.6-rc5) seems to be needed for 5.4 and 5.5
> > > branches:
> > >
> > > commit 6d390e4b5d48ec03bb87e63cf0a2bff5f4e116da
> > > Author: yangerkun <yangerkun@huawei.com>
> > > Date: Wed Mar 4 15:25:56 2020 +0800
> > >
> > > locks: fix a potential use-after-free problem when wakeup a waiter
> >
> > I've queued it up for 5.5 and 5.4, thanks!
> >
> > > I'm a bit surprised that it hasn't yet been applied, while some fixes
> > > from 5.6-rc6 have.
> >
> > Greg, I wonder if it makes sense to have you push a "Greg is here
> > --->" "bookmark" in the form of a tag/branch on linux-stable-rc.git? at
> > the very least it'll make it easy to see if something was missed or
> > still waiting in the queue.
>
> To quote Jeff Layton:
>
> Hi Greg, there is a performance regression with this patch. We're
> sorting through potential ways to address it at the moment, but you may
> want to hold off until we have a fix for that merged.
>
> Sorry for the hassle!
>
> Which is why I dropped it for now.
>
> I'll go drop it again :)

I didn't see any mention of this on the stable list though.
I also don't think that a performance regression outweighs the
seriousness of the bug being fixed.

Ben.

--
Ben Hutchings, Software Developer Codethink Ltd
https://www.codethink.co.uk/ Dale House, 35 Dale Street
Manchester, M1 2HF, United Kingdom