linux-kernel - Re: Kernel version numbers after 4.9.255 and 4.4.255

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Date:   Sat, 6 Feb 2021 08:23:06 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Jiri Slaby <jirislaby@...nel.org>,
        Jari Ruusu <jariruusu@...tonmail.com>,
        Sasha Levin <sashal@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        masahiroy@...nel.org
Subject: Re: Kernel version numbers after 4.9.255 and 4.4.255

On Fri, Feb 05, 2021 at 07:44:12PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > > Ugh, I thought this was an internal representation, not an external one
> > > > :(
> > > > 
> > > > > It might work somewhere, but there are a lot of (X * 65536 + Y * 256 + Z)
> > > > > assumptions all around the world. So this doesn't look like a good idea.
> > > > 
> > > > Ok, so what happens if we "wrap"?  What will break with that?  At first
> > > > glance, I can't see anything as we keep the padding the same, and our
> > > > build scripts seem to pick the number up from the Makefile and treat it
> > > > like a string.
> > > > 
> > > > It's only the crazy out-of-tree kernel stuff that wants to do minor
> > > > version checks that might go boom.  And frankly, I'm not all that
> > > > concerned if they have problems :)
> > > > 
> > > > So, let's leave it alone and just see what happens!
> > > 
> > > Yeah, stable is a great place to do the experiments. Not that this is
> > > the first time :-(.
> > 
> > How else can we "test this out"?
> > 
> > Should I do an "empty" release of 4.4.256 and see if anyone complains?
> 
> It seems that would be bad idea, as it would cause problems when stuff
> is compiled on 4.4.256, not simply by running it.
> 
> Sasha's patch seems like one option that could work.
> 
> Even safer option is to switch to 4.4.255-st1, 4.4.255-st2 ... scheme.

Using EXTRAVERSION would work, but it is effectivly the same thing as
nothing exports that to userspace through the LINUX_VERSION macro.

So clamping the version like Sasha's patches seems to be the best
solution.

thanks,

greg k-h