Right now SUBLEVEL is overflowing, and some userspace may start treating 4.9.256 as 4.10. While out of tree modules have different ways of extracting the version number (and we're generally ok with breaking them), we do care about breaking userspace and it would appear that this overflow might do just that.

Our rules around userspace ABI in the stable kernel are pretty simple: we don't break it. Thus, while userspace may be checking major/minor, it shouldn't be doing anything with sublevel.

This patch applies a big band-aid to the 4.9 and 4.4 kernels in the form of clamping their sublevel to 255.

The clamp is done for the purpose of LINUX_VERSION_CODE only, and extracting the version number from the Makefile or "make kernelversion" will continue to work as intended.

We might need to do it later in newer trees, but maybe we'll have a better solution by then, so I'm ignoring that problem for now.

Signed-off-by: Sasha Levin sashal@kernel.org --- Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile b/Makefile index 69af44d3dcd14..93f7ce06fc8c9 100644 --- a/Makefile +++ b/Makefile @@ -1141,7 +1141,7 @@ endef

define filechk_version.h (echo #define LINUX_VERSION_CODE $(shell \ - expr $(VERSION) * 65536 + 0$(PATCHLEVEL) * 256 + 0$(SUBLEVEL)); \ + expr $(VERSION) * 65536 + 0$(PATCHLEVEL) * 256 + 255); \ echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))';) endef