1 files changed, 98 insertions, 0 deletions

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 5838fa911aa0..8ec57c07b125 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -542,5 +542,103 @@ extern struct movsl_mask {
 # include <asm/uaccess_64.h>
 #endif
 
+unsigned long __must_check _copy_from_user(void *to, const void __user *from,
+                                           unsigned n);
+unsigned long __must_check _copy_to_user(void __user *to, const void *from,
+                                         unsigned n);
+
+#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
+# define copy_user_diag __compiletime_error
+#else
+# define copy_user_diag __compiletime_warning
+#endif
+
+extern void copy_user_diag("copy_from_user() buffer size is too small")
+copy_from_user_overflow(void);
+extern void copy_user_diag("copy_to_user() buffer size is too small")
+copy_to_user_overflow(void) __asm__("copy_from_user_overflow");
+
+#undef copy_user_diag
+
+#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
+
+extern void
+__compiletime_warning("copy_from_user() buffer size is not provably correct")
+__copy_from_user_overflow(void) __asm__("copy_from_user_overflow");
+#define __copy_from_user_overflow(size, count) __copy_from_user_overflow()
+
+extern void
+__compiletime_warning("copy_to_user() buffer size is not provably correct")
+__copy_to_user_overflow(void) __asm__("copy_from_user_overflow");
+#define __copy_to_user_overflow(size, count) __copy_to_user_overflow()
+
+#else
+
+static inline void
+__copy_from_user_overflow(int size, unsigned long count)
+{
+        WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
+}
+
+#define __copy_to_user_overflow __copy_from_user_overflow
+
+#endif
+
+static inline unsigned long __must_check
+copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+        int sz = __compiletime_object_size(to);
+
+        might_fault();
+
+        /*
+         * While we would like to have the compiler do the checking for us
+         * even in the non-constant size case, any false positives there are
+         * a problem (especially when DEBUG_STRICT_USER_COPY_CHECKS, but even
+         * without - the [hopefully] dangerous looking nature of the warning
+         * would make people go look at the respecitive call sites over and
+         * over again just to find that there's no problem).
+         *
+         * And there are cases where it's just not realistic for the compiler
+         * to prove the count to be in range. For example when multiple call
+         * sites of a helper function - perhaps in different source files -
+         * all doing proper range checking, yet the helper function not doing
+         * so again.
+         *
+         * Therefore limit the compile time checking to the constant size
+         * case, and do only runtime checking for non-constant sizes.
+         */
+
+        if (likely(sz < 0 || sz >= n))
+                n = _copy_from_user(to, from, n);
+        else if(__builtin_constant_p(n))
+                copy_from_user_overflow();
+        else
+                __copy_from_user_overflow(sz, n);
+
+        return n;
+}
+
+static inline unsigned long __must_check
+copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+        int sz = __compiletime_object_size(from);
+
+        might_fault();
+
+        /* See the comment in copy_from_user() above. */
+        if (likely(sz < 0 || sz >= n))
+                n = _copy_to_user(to, from, n);
+        else if(__builtin_constant_p(n))
+                copy_to_user_overflow();
+        else
+                __copy_to_user_overflow(sz, n);
+
+        return n;
+}
+
+#undef __copy_from_user_overflow
+#undef __copy_to_user_overflow
+
 #endif /* _ASM_X86_UACCESS_H */