Re: Linux 4.4.256

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Feb 05, 2021 at 12:56:58PM -0800, Guenter Roeck wrote:
> On Fri, Feb 05, 2021 at 03:26:36PM +0100, Greg Kroah-Hartman wrote:
> > I'm announcing the release of the 4.4.256 kernel.
> > 
> > This, and the 4.9.256 release are a little bit "different" than normal.
> > 
> > This contains only 1 patch, just the version bump from .255 to .256 which ends
> > up causing the userspace-visable LINUX_VERSION_CODE to behave a bit differently
> > than normal due to the "overflow".
> > 
> > With this release, KERNEL_VERSION(4, 4, 256) is the same as KERNEL_VERSION(4, 5, 0).
> > 
> > Nothing in the kernel build itself breaks with this change, but given that this
> > is a userspace visible change, and some crazy tools (like glibc and gcc) have
> > logic that checks the kernel version for different reasons, I wanted to do this
> > release as an "empty" release to ensure that everything still works properly.
> > 
> > So, this is a YOU MUST UPGRADE requirement of a release.  If you rely on the
> > 4.4.y kernel, please throw this release into your test builds and rebuild the
> > world and let us know if anything breaks, or if all is well.
> > 
> > Go forth and do full system rebuilds!  Yocto and Gentoo are great for this, as
> > will systems that use buildroot.
> > 
> > I'll try to hold off on doing a "real" 4.4.y release for a week to give
> > everyone a chance to test this out and get back to me.  The pending patches in
> > the 4.4.y queue are pretty serious, so I am loath to wait longer than that,
> > consider yourself warned...
> > 
> Thanks a lot for the heads-up. For chromeos-4.4, the version number wrap
> is indeed fatal: Unfortunately we have lots of vendor code in the tree
> which uses KERNEL_VERSION(), and all the version comparisons against
> KERNEL_VERSION(4,5,0) do result in compile errors.
> 
> The best workaround/hack/kludge to address the problem seems to be the idea
> to use 4.4.255 as version number for LINUX_VERSION_CODE and KERNEL_VERSION()
> if SUBLEVEL is larger than 255. Did anyone find a better solution for the
> problem ?

I think Sasha's patch here:
	https://lore.kernel.org/r/20210205174702.1904681-1-sashal@kernel.org
is looking like the solution.

thanks,

greg k-h