From: Sasha Levin > Sent: 06 February 2021 03:51 > > Right now if SUBLEVEL becomes larger than 255 it will overflow into the > territory of PATCHLEVEL, causing havoc in userspace that tests for > specific kernel version. > > While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test > SUBLEVEL at any point as ABI changes don't happen in the context of > stable tree. > > Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in > the context of LINUX_VERSION_CODE. This does not affect "make > kernelversion" and such. > > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > Makefile | 12 +++++++++--- > 1 file changed, 9 insertions(+), 3 deletions(-) > > diff --git a/Makefile b/Makefile > index 49ac1b7fe8e99..157be50c691e5 100644 > --- a/Makefile > +++ b/Makefile > @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h > endef > > define filechk_version.h > - echo \#define LINUX_VERSION_CODE $(shell \ > - expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \ > - echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))' > + if [ $(SUBLEVEL) -gt 255 ]; then \ > + echo \#define LINUX_VERSION_CODE $(shell \ > + expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \ > + else \ > + echo \#define LINUX_VERSION_CODE $(shell \ > + expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \ > + fi; \ > + echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + \ > + ((c) > 255 ? 255 : (c)))' > endef Why not use KERNEL_VERSION to define LINUX_VERSION_CODE ? Basically just: echo '#define LINUX_VERSION_CODE KERNEL_VERSION($(VERSION), $(PATCHLEVEL)+0, $(SUBLEVEL)+0)' If PATCHLEVEL and SUBLEVEL are guaranteed to be non-empty the +0 can be removed. The patch assumes they are non-empty, the original pre-prended 0 to stop syntax error for empty version strings. Note that the expr version will process 08 and 09. gcc will treat them as octal, and may error them. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
