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    SubjectRe: [PATCH] compiler_types.h: Test for __alloc_size__ again
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    On 9/29/22 10:16, Kees Cook wrote:
    > While the "alloc_size" attribute is available on all GCC versions, I
    > forgot that it gets disabled explicitly by the kernel in GCC < 9.1 due
    > to misbehaviors. Add a note to the compiler_attributes.h entry for it,
    > and restore the #ifdef in compiler_types.h.
    >
    > Cc: Vlastimil Babka <vbabka@suse.cz>
    > Cc: Miguel Ojeda <ojeda@kernel.org>
    > Cc: Nick Desaulniers <ndesaulniers@google.com>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: Yonghong Song <yhs@fb.com>
    > Cc: Hao Luo <haoluo@google.com>
    > Cc: Marco Elver <elver@google.com>
    > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
    > Link: https://lore.kernel.org/lkml/CAMuHMdXK+UN1YVZm9DenuXAM8hZRUZJwp=SXsueP7sWiVU3a9A@mail.gmail.com
    > Fixes: 63caa04ec60583b1 ("slab: Remove __malloc attribute from realloc functions")
    > Signed-off-by: Kees Cook <keescook@chromium.org>

    Thanks, I decided to late squash it so we don't needlessly cause issues for
    people doing bisections with gcc-8 later.

    > ---
    > I swear I sent this earlier today, but I don't see it on lore still. Resending,
    > so apologies if this is a duplicate.
    > ---
    > include/linux/compiler_attributes.h | 3 ++-
    > include/linux/compiler_types.h | 9 +++++++--
    > 2 files changed, 9 insertions(+), 3 deletions(-)
    >
    > diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
    > index 465be5f072ff..55fbb6091ecf 100644
    > --- a/include/linux/compiler_attributes.h
    > +++ b/include/linux/compiler_attributes.h
    > @@ -65,7 +65,8 @@
    >
    > /*
    > * Note: do not use this directly. Instead, use __alloc_size() since it is conditionally
    > - * available and includes other attributes.
    > + * available and includes other attributes. For GCC < 9.1, __alloc_size__ gets undefined
    > + * in compiler-gcc.h, due to misbehaviors.
    > *
    > * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute
    > * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size
    > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
    > index f141a6f6b9f6..0717534f8364 100644
    > --- a/include/linux/compiler_types.h
    > +++ b/include/linux/compiler_types.h
    > @@ -275,8 +275,13 @@ struct ftrace_likely_data {
    > * be performing a _reallocation_, as that may alias the existing pointer.
    > * For these, use __realloc_size().
    > */
    > -#define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
    > -#define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__)
    > +#ifdef __alloc_size__
    > +# define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
    > +# define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__)
    > +#else
    > +# define __alloc_size(x, ...) __malloc
    > +# define __realloc_size(x, ...)
    > +#endif
    >
    > #ifndef asm_volatile_goto
    > #define asm_volatile_goto(x...) asm goto(x)

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