Re: Fwd: Memory corruption in multithreaded user space program while calling fork

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Jul 04, 2023 at 01:22:54PM -0700, Suren Baghdasaryan wrote:
> On Tue, Jul 4, 2023 at 9:18 AM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Tue, 4 Jul 2023 09:00:19 +0100 Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > > > > > > Thanks! I'll investigate this later today. After discussing with
> > > > > > > Andrew, we would like to disable CONFIG_PER_VMA_LOCK by default until
> > > > > > > the issue is fixed. I'll post a patch shortly.
> > > > > >
> > > > > > Posted at: https://lore.kernel.org/all/20230703182150.2193578-1-surenb@google.com/
> > > > >
> > > > > As that change fixes something in 6.4, why not cc: stable on it as well?
> > > >
> > > > Sorry, I thought since per-VMA locks were introduced in 6.4 and this
> > > > patch is fixing 6.4 I didn't need to send it to stable for older
> > > > versions. Did I miss something?
> > >
> > > 6.4.y is a stable kernel tree right now, so yes, it needs to be included
> > > there :)
> >
> > I'm in wait-a-few-days-mode on this.  To see if we have a backportable
> > fix rather than disabling the feature in -stable.
> 
> Ok, I think we have a fix posted at [2]  and it's cleanly applies to
> 6.4.y stable branch as well. However fork() performance might slightly
> regress, therefore disabling per-VMA locks by default for now seems to
> be preferable even with this fix (see discussion at
> https://lore.kernel.org/all/54cd9ffb-8f4b-003f-c2d6-3b6b0d2cb7d9@google.com/).
> IOW, both [1] and [2] should be applied to 6.4.y stable. Both apply
> cleanly and I CC'ed stable on [2]. Greg, should I send [1] separately
> to stable@vger?

We can't do anything for stable until it lands in Linus's tree, so if
you didn't happen to have the stable@ tag in the patch, just email us
the git SHA1 and I can pick it up that way.

thanks,

greg k-h