x86: Add a Kconfig option to turn the copy_from_user warnings into errors
For automated testing it is useful to have the option to turn
the warnings on copy_from_user() etc checks into errors:
In function ‘copy_from_user’,
inlined from ‘fd_copyin’ at drivers/block/floppy.c:3080,
inlined from ‘fd_ioctl’ at drivers/block/floppy.c:3503:
linux/arch/x86/include/asm/uaccess_32.h:213:
error: call to ‘copy_from_user_overflow’ declared with attribute error:
copy_from_user buffer size is not provably correct
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20091002075050.4e9f7641@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index d105f29..1bd2e36f 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -287,4 +287,18 @@
If unsure, say N.
+config DEBUG_STRICT_USER_COPY_CHECKS
+ bool "Strict copy size checks"
+ depends on DEBUG_KERNEL
+ ---help---
+ Enabling this option turns a certain set of sanity checks for user
+ copy operations into compile time failures.
+
+ The copy_from_user() etc checks are there to help test if there
+ are sufficient security checks on the length argument of
+ the copy operation, by having gcc prove that the argument is
+ within bounds.
+
+ If unsure, or if you run an older (pre 4.4) gcc, say N.
+
endmenu
diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h
index 952f9e7..0c9825e 100644
--- a/arch/x86/include/asm/uaccess_32.h
+++ b/arch/x86/include/asm/uaccess_32.h
@@ -193,7 +193,9 @@
extern void copy_from_user_overflow(void)
-#ifdef CONFIG_DEBUG_STACKOVERFLOW
+#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
+ __compiletime_error("copy_from_user() buffer size is not provably correct")
+#else
__compiletime_warning("copy_from_user() buffer size is not provably correct")
#endif
;
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index f1709c1..77542c5 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -41,4 +41,5 @@
#define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
#if __GNUC_MINOR__ >= 4
#define __compiletime_warning(message) __attribute__((warning(message)))
+#define __compiletime_error(message) __attribute__((error(message)))
#endif
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 9503563..88fd4b6 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -273,6 +273,9 @@
#ifndef __compiletime_warning
# define __compiletime_warning(message)
#endif
+#ifndef __compiletime_error
+# define __compiletime_error(message)
+#endif
/*
* Prevent the compiler from merging or refetching accesses. The compiler