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From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
	Miguel Ojeda <ojeda@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Daniel Micay <danielmicay@gmail.com>,
	Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Vlastimil Babka <vbabka@suse.cz>, Dennis Zhou <dennis@kernel.org>,
	Tejun Heo <tj@kernel.org>, Masahiro Yamada <masahiroy@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	linux-mm@kvack.org, linux-kbuild@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: [PATCH 1/5] Compiler Attributes: Add __alloc_size() for better bounds checking
Date: Tue, 17 Aug 2021 22:08:37 -0700	[thread overview]
Message-ID: <20210818050841.2226600-2-keescook@chromium.org> (raw)
In-Reply-To: <20210818050841.2226600-1-keescook@chromium.org>

GCC and Clang can use the alloc_size attribute to better inform the
results of __builtin_object_size() (for compile-time constant values).
Clang can additionally use alloc_size to informt the results of
__builtin_dynamic_object_size() (for run-time values).

Additionally disables -Wno-alloc-size-larger-than since the allocators
already reject SIZE_MAX, and the compile-time warnings aren't helpful.

Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: clang-built-linux@googlegroups.com
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 Makefile                            | 6 +++++-
 include/linux/compiler_attributes.h | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 1b238ce86ed4..3b6fb740584e 100644
--- a/Makefile
+++ b/Makefile
@@ -1076,9 +1076,13 @@ KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
 # Another good warning that we'll want to enable eventually
 KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
 
-# Enabled with W=2, disabled by default as noisy
 ifdef CONFIG_CC_IS_GCC
+# Enabled with W=2, disabled by default as noisy
 KBUILD_CFLAGS += -Wno-maybe-uninitialized
+
+# 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
 endif
 
 # disable invalid "can't wrap" optimizations for signed / pointers
diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index 67c5667f8042..203b0ac62d15 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -54,6 +54,12 @@
 #define __aligned(x)                    __attribute__((__aligned__(x)))
 #define __aligned_largest               __attribute__((__aligned__))
 
+/*
+ *   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
+ */
+#define __alloc_size(x, ...)		__attribute__((__alloc_size__(x, ## __VA_ARGS__)))
+
 /*
  * Note: users of __always_inline currently do not write "inline" themselves,
  * which seems to be required by gcc to apply the attribute according
-- 
2.30.2


  reply	other threads:[~2021-08-18  5:09 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18  5:08 [PATCH 0/5] " Kees Cook
2021-08-18  5:08 ` Kees Cook [this message]
2021-08-18 13:07   ` [PATCH 1/5] Compiler Attributes: " Miguel Ojeda
2021-08-18 17:58     ` Kees Cook
2021-08-18 18:04   ` Nathan Chancellor
2021-08-18 21:04     ` Kees Cook
2021-08-18  5:08 ` [PATCH 2/5] slab: Add __alloc_size attributes " Kees Cook
2021-08-18  5:31   ` Joe Perches
2021-08-18  6:16     ` Kees Cook
2021-08-18  6:30       ` Joe Perches
2021-08-19  0:27     ` Matthew Wilcox
2021-08-19  1:10       ` Joe Perches
2021-08-19  2:16         ` Matthew Wilcox
2021-08-19  2:59           ` Joe Perches
2021-08-18  5:08 ` [PATCH 3/5] mm/page_alloc: " Kees Cook
2021-08-18  5:08 ` [PATCH 4/5] percpu: " Kees Cook
2021-08-18  5:08 ` [PATCH 5/5] mm/vmalloc: " Kees Cook
2021-08-19  9:09 ` [PATCH 0/5] Add __alloc_size() " Christoph Hellwig
2021-08-19 14:18   ` Daniel Micay
2021-08-25 10:01     ` Christoph Lameter
2021-08-25 16:34       ` Kees Cook

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