On Tue, Oct 01, 2024 at 06:47:59PM +0200, Aleksandr Nogikh wrote:
> Hi Ido,
>
> On Tue, 1 Oct 2024 16:38:39 +0300, Ido Schimmel wrote:
> >
> > On Tue, Oct 01, 2024 at 02:11:27PM +0200, Greg KH wrote:
> > > On Tue, Oct 01, 2024 at 02:20:35PM +0300, Ido Schimmel wrote:
> > > > I read the stable rules and I am not providing an "upstream commit ID"
> > > > since the code in upstream has been reworked, making this fix
> > > > irrelevant. The only affected stable kernel is 6.1.y.
> > >
> > > You need to document the heck out of why this is only relevant for this
> > > one specific kernel branch IN the changelog text, so that we understand
> > > what is going on, AND you need to get acks from the relevant maintainers
> > > of this area of the kernel to accept something that is not in Linus's
> > > tree.
> > >
> > > But first of, why? Why not just take the upstrema commits instead?
> >
> > There were a lot of changes as part of the 6.3 cycle to completely
> > rework the semantics of the devlink instance reference count. As part of
> > these changes, commit d77278196441 ("devlink: bump the instance index
> > directly when iterating") inadvertently fixed the bug mentioned in this
> > patch. This commit cannot be applied to 6.1.y as-is because a prior
> > commit (also in 6.3) moved the code to a different file (leftover.c ->
> > core.c). There might be more dependencies that I'm currently unaware of.
> >
> > The alternative, proposed in this patch, is to provide a minimal and
> > contained fix for the bug introduced in upstream commit c2368b19807a
> > ("net: devlink: introduce "unregistering" mark and use it during
> > devlinks iteration") as part of the 6.0 cycle.
> >
> > The above explains why the patch is only relevant to 6.1.y.
>
> Thanks for bringing up this topic!
>
> For what it's worth, syzbot would also greatly benefit from your fix:
> https://github.com/google/syzkaller/issues/5328
>
> I've built a kernel locally with your changes, run syzkaller against it,
> and I can confirm that the kernel no longer crashes due to devlink.
Good to know :)
I hope this patch can be accepted as-is instead of a much larger patch.
Will copy you on the next version.
Thanks for testing!
