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Subject[PATCH] compiler_types.h: Test for __alloc_size__ again
Date
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>
---
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)
--
2.34.1
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