linux-kernel - Re: [PATCH] Kbuild: Enable the gcc flag -Wformat-security (was: Re: [PATCH] Kbuild: Disable the -Wformat-security gcc flag)

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Date:	Thu, 5 Feb 2009 09:57:28 +0100
From:	Floris Kraak <randakar@...il.com>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Robert Hancock <hancockrwd@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Trivial Patch Monkey <trivial@...nel.org>,
	Roland Dreier <rdreier@...co.com>
Subject: Re: [PATCH] Kbuild: Enable the gcc flag -Wformat-security (was: Re: 
	[PATCH] Kbuild: Disable the -Wformat-security gcc flag)

On Thu, Feb 5, 2009 at 9:47 AM, Floris Kraak <randakar@...il.com> wrote:
>
> Here goes:
>

Resend, seems like the earlier patch doesn't quite actually work as
advertised; -Wformat-security needs -Wformat enabled as well.
---
[PATCH] Kbuild: Enable the gcc flag -Wformat-security

Some distributions have enabled the gcc flag -Wformat-security by
default. This causes about 150 new warnings to show up in an
allyesconfig kernel build that are never seen by the majority of the
developers. However there is some value to having this warning. In
some cases there are potential (security) bugs involved where
malicious or simply malformed data from outside the kernel could
trigger stack overflows or other nastyness.
Instead of having a cleanup team running around in perpetuity going
over all new format strings in code it's better to just emit the
warning in all cases.

Signed-off-by: Floris Kraak <randakar@...il.com>
---
diff --git a/Makefile b/Makefile
index 7715b2c..d186e41 100644
--- a/Makefile
+++ b/Makefile
@@ -346,7 +346,8 @@ KBUILD_CPPFLAGS := -D__KERNEL__

 KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		   -fno-strict-aliasing -fno-common \
-		   -Werror-implicit-function-declaration
+		   -Werror-implicit-function-declaration \
+		   -Wformat -Wformat-security
 KBUILD_AFLAGS   := -D__ASSEMBLY__

 # Read KERNELRELEASE from include/config/kernel.release (if it exists)
---
"They that give up essential liberty to obtain temporary safety,
deserve neither liberty nor safety."
  -- Ben Franklin

"The course of history shows that as a government grows, liberty
decreases."
  -- Thomas Jefferson
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