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kbuild: clamp SUBLEVEL to 255

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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@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Sasha Levin 2021-02-05 22:50:32 -05:00 committed by Masahiro Yamada
parent 98cd6f521f
commit 9b82f13e7e
1 changed files with 9 additions and 3 deletions
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12
Makefile
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@ -1247,9 +1247,15 @@ 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
$(version_h): FORCE