Adjust the warning logic to deal with pre-9.1 gcc behaviors. Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Tested-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- Hi Andrew, this is meant to replace: compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix.patch Thanks! --- Makefile | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index 41ed29b5af2b..141a851930e6 100644 --- a/Makefile +++ b/Makefile @@ -1096,8 +1096,17 @@ endif ifdef CONFIG_CC_IS_GCC # The allocators already balk at large sizes, so silence the compiler -# warnings for bounds checks involving those possible values. -KBUILD_CFLAGS += -Wno-alloc-size-larger-than +# warnings for bounds checks involving those possible values. While +# -Wno-alloc-size-larger-than would normally be used here, earlier versions +# of gcc (<9.1) weirdly don't handle the option correctly when _other_ +# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX +# doesn't work (as it is documented to), silently resolving to "0" prior to +# version 9.1 (and producing an error more recently). Numeric values larger +# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently +# ignored, continuing to default to PTRDIFF_MAX. So, left with no other +# choice, we must perform a versioned check to disable this warning. +# https://lore.kernel.org/lkml/20210824115859.187f272f@xxxxxxxxxxxxxxxx +KBUILD_CFLAGS += $(call cc-ifversion, -ge, 0901, -Wno-alloc-size-larger-than) endif # disable invalid "can't wrap" optimizations for signed / pointers -- 2.30.2
