sparc/uaccess: Enable hardened usercopy

Enables CONFIG_HARDENED_USERCOPY checks on sparc.

Based on code from PaX and grsecurity.
Signed-off-by: Kees Cook <keescook@chromium.org>

arch/sparc/Kconfig

@@ -43,6 +43,7 @@ config SPARC
 	select OLD_SIGSUSPEND
 	select ARCH_HAS_SG_CHAIN
 	select CPU_NO_EFFICIENT_FFS
+	select HAVE_ARCH_HARDENED_USERCOPY
 
 config SPARC32
 	def_bool !64BIT

arch/sparc/include/asm/uaccess_32.h

@@ -248,22 +248,28 @@ unsigned long __copy_user(void __user *to, const void __user *from, unsigned lon
 
 static inline unsigned long copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	if (n && __access_ok((unsigned long) to, n))
+	if (n && __access_ok((unsigned long) to, n)) {
+		if (!__builtin_constant_p(n))
+			check_object_size(from, n, true);
 		return __copy_user(to, (__force void __user *) from, n);
-	else
+	} else
 		return n;
 }
 
 static inline unsigned long __copy_to_user(void __user *to, const void *from, unsigned long n)
 {
+	if (!__builtin_constant_p(n))
+		check_object_size(from, n, true);
 	return __copy_user(to, (__force void __user *) from, n);
 }
 
 static inline unsigned long copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	if (n && __access_ok((unsigned long) from, n))
+	if (n && __access_ok((unsigned long) from, n)) {
+		if (!__builtin_constant_p(n))
+			check_object_size(to, n, false);
 		return __copy_user((__force void __user *) to, from, n);
-	else
+	} else
 		return n;
 }
 

arch/sparc/include/asm/uaccess_64.h

@@ -210,8 +210,12 @@ unsigned long copy_from_user_fixup(void *to, const void __user *from,
 static inline unsigned long __must_check
 copy_from_user(void *to, const void __user *from, unsigned long size)
 {
-	unsigned long ret = ___copy_from_user(to, from, size);
+	unsigned long ret;
 
+	if (!__builtin_constant_p(size))
+		check_object_size(to, size, false);
+
+	ret = ___copy_from_user(to, from, size);
 	if (unlikely(ret))
 		ret = copy_from_user_fixup(to, from, size);
 
@@ -227,8 +231,11 @@ unsigned long copy_to_user_fixup(void __user *to, const void *from,
 static inline unsigned long __must_check
 copy_to_user(void __user *to, const void *from, unsigned long size)
 {
-	unsigned long ret = ___copy_to_user(to, from, size);
+	unsigned long ret;
 
+	if (!__builtin_constant_p(size))
+		check_object_size(from, size, true);
+	ret = ___copy_to_user(to, from, size);
 	if (unlikely(ret))
 		ret = copy_to_user_fixup(to, from, size);
 	return ret;