The patch titled
Subject: Compiler Attributes: Add __alloc_size for better bounds checking fix
has been added to the -mm tree. Its filename is
compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix-2.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix-2.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix-2.patch
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------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: Compiler Attributes: Add __alloc_size for better bounds checking fix
Adjust the warning logic to deal with pre-9.1 gcc behaviors.
Link: https://lkml.kernel.org/r/20210827151327.2729736-1-keescook@xxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Tested-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Makefile | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/Makefile~compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix-2
+++ a/Makefile
@@ -1094,8 +1094,17 @@ 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
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
compiler-attributes-add-__alloc_size-for-better-bounds-checking.patch
compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix-2.patch
compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix.patch
compiler-attributes-add-__alloc_size-for-better-bounds-checking-fix-fix.patch
checkpatch-add-__alloc_size-to-known-attribute.patch
slab-clean-up-function-declarations.patch
slab-add-__alloc_size-attributes-for-better-bounds-checking.patch
mm-page_alloc-add-__alloc_size-attributes-for-better-bounds-checking.patch
percpu-add-__alloc_size-attributes-for-better-bounds-checking.patch
mm-vmalloc-add-__alloc_size-attributes-for-better-bounds-checking.patch
