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From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Bart van Assche <bvanassche@acm.org>,
	Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	Alexander Potapenko <glider@google.com>,
	Joe Perches <joe@perches.com>, Andy Whitcroft <apw@canonical.com>,
	x86@kernel.org, drbd-dev@lists.linbit.com,
	linux-block@vger.kernel.org, b43-dev@lists.infradead.org,
	netdev@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-wireless@vger.kernel.org, linux-ide@vger.kernel.org,
	linux-clk@vger.kernel.org, linux-spi@vger.kernel.org,
	linux-mm@kvack.org, clang-built-linux@googlegroups.com
Subject: [PATCH v2 16/16] compiler: Remove uninitialized_var() macro
Date: Fri, 19 Jun 2020 20:30:06 -0700
Message-ID: <20200620033007.1444705-16-keescook@chromium.org> (raw)
In-Reply-To: <20200620033007.1444705-1-keescook@chromium.org>

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

As recommended[2] by[3] Linus[4], remove the macro. With the recent
change to disable -Wmaybe-uninitialized in v5.7 in commit 78a5255ffb6a
("Stop the ad-hoc games with -Wno-maybe-initialized"), this is likely
the best time to make this treewide change.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Bart van Assche <bvanassche@acm.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/compiler-clang.h | 2 --
 include/linux/compiler-gcc.h   | 6 ------
 tools/include/linux/compiler.h | 2 --
 tools/virtio/linux/kernel.h    | 2 --
 4 files changed, 12 deletions(-)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index ee37256ec8bd..f2371b83aaf2 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -5,8 +5,6 @@
 
 /* Compiler specific definitions for Clang compiler */
 
-#define uninitialized_var(x) x = *(&(x))
-
 /* same as gcc, this was present in clang-2.6 so we can assume it works
  * with any version that can compile the kernel
  */
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 7dd4e0349ef3..84e099a87383 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -59,12 +59,6 @@
 	(typeof(ptr)) (__ptr + (off));					\
 })
 
-/*
- * A trick to suppress uninitialized variable warning without generating any
- * code
- */
-#define uninitialized_var(x) x = x
-
 #ifdef CONFIG_RETPOLINE
 #define __noretpoline __attribute__((__indirect_branch__("keep")))
 #endif
diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 9f9002734e19..2f2f4082225e 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -111,8 +111,6 @@
 # define noinline
 #endif
 
-#define uninitialized_var(x) x = *(&(x))
-
 #include <linux/types.h>
 
 /*
diff --git a/tools/virtio/linux/kernel.h b/tools/virtio/linux/kernel.h
index 6683b4a70b05..1e14ab967c11 100644
--- a/tools/virtio/linux/kernel.h
+++ b/tools/virtio/linux/kernel.h
@@ -109,8 +109,6 @@ static inline void free_page(unsigned long addr)
 	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
 	(type *)( (char *)__mptr - offsetof(type,member) );})
 
-#define uninitialized_var(x) x = x
-
 # ifndef likely
 #  define likely(x)	(__builtin_expect(!!(x), 1))
 # endif
-- 
2.25.1


  parent reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-20  3:29 [PATCH v2 00/16] " Kees Cook
2020-06-20  3:29 ` [PATCH v2 01/16] docs: deprecated.rst: Add uninitialized_var() Kees Cook
2020-06-22 16:59   ` Nick Desaulniers
2020-06-20  3:29 ` [PATCH v2 02/16] x86/mm/numa: Remove uninitialized_var() usage Kees Cook
2020-06-20  3:29 ` [PATCH v2 03/16] drbd: " Kees Cook
2020-06-20  3:29 ` [PATCH v2 04/16] b43: " Kees Cook
2020-06-22 17:04   ` Nick Desaulniers
2020-06-22 21:04     ` Kees Cook
2020-06-23 18:29       ` Nick Desaulniers
2020-07-15 10:37   ` Kalle Valo
2020-06-20  3:29 ` [PATCH v2 05/16] rtlwifi: rtl8192cu: " Kees Cook
2020-06-20  3:29 ` [PATCH v2 06/16] ide: " Kees Cook
2020-06-20  3:29 ` [PATCH v2 07/16] clk: st: " Kees Cook
2020-06-22  9:03   ` Stephen Boyd
2020-06-20  3:29 ` [PATCH v2 08/16] spi: davinci: " Kees Cook
2020-07-01 20:39   ` Mark Brown
2020-07-02 15:21     ` Kees Cook
2020-07-02 15:23       ` Mark Brown
2020-07-02 15:42         ` Kees Cook
2020-07-02 16:23           ` Joe Perches
2020-06-20  3:30 ` [PATCH v2 09/16] clk: spear: " Kees Cook
2020-06-22  9:03   ` Stephen Boyd
2020-06-20  3:30 ` [PATCH v2 10/16] KVM: PPC: Book3S PR: " Kees Cook
2020-06-22 17:22   ` Nick Desaulniers
2020-06-20  3:30 ` [PATCH v2 11/16] media: sur40: " Kees Cook
2020-06-22 18:39   ` Nick Desaulniers
2020-06-20  3:30 ` [PATCH v2 12/16] f2fs: Eliminate usage of uninitialized_var() macro Kees Cook
2020-06-20  3:30 ` [PATCH v2 14/16] checkpatch: Remove awareness " Kees Cook
2020-06-20  3:30 ` [PATCH v2 15/16] treewide: Remove uninitialized_var() usage Kees Cook
2020-06-20  3:30 ` Kees Cook [this message]
2020-06-20  3:30 ` [PATCH v2 13/16] mm/debug_vm_pgtable: " Kees Cook
2020-06-22 17:27   ` Nick Desaulniers
2020-06-20  7:03 ` [PATCH v2 00/16] Remove uninitialized_var() macro Sedat Dilek
2020-06-20 15:57   ` Kees Cook
2020-06-22  9:07     ` Sedat Dilek

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