4 files changed, 22 insertions, 3 deletions

diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h
index 582d6aef7417..952f9e793c3e 100644
--- a/arch/x86/include/asm/uaccess_32.h
+++ b/arch/x86/include/asm/uaccess_32.h
@@ -191,6 +191,13 @@ unsigned long __must_check _copy_from_user(void *to,
                                           const void __user *from,
                                           unsigned long n);
 
+
+extern void copy_from_user_overflow(void)
+#ifdef CONFIG_DEBUG_STACKOVERFLOW
+        __compiletime_warning("copy_from_user() buffer size is not provably correct")
+#endif
+;
+
 static inline unsigned long __must_check copy_from_user(void *to,
                                           const void __user *from,
                                           unsigned long n)
@@ -200,10 +207,9 @@ static inline unsigned long __must_check copy_from_user(void *to,
 
         if (likely(sz == -1 || sz >= n))
                 ret = _copy_from_user(to, from, n);
-#ifdef CONFIG_DEBUG_VM
         else
-                WARN(1, "Buffer overflow detected!\n");
-#endif
+                copy_from_user_overflow();
+
         return ret;
 }
 
diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index 8498684e45b0..e218d5df85ff 100644
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -883,3 +883,9 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
         return n;
 }
 EXPORT_SYMBOL(_copy_from_user);
+
+void copy_from_user_overflow(void)
+{
+        WARN(1, "Buffer overflow detected!\n");
+}
+EXPORT_SYMBOL(copy_from_user_overflow);
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index a3aef5d55dba..f1709c1f9eae 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -39,3 +39,6 @@
 #endif
 
 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
+#if __GNUC_MINOR__ >= 4
+#define __compiletime_warning(message) __attribute__((warning(message)))
+#endif
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 8e54108688f9..950356311f12 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -270,6 +270,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 #ifndef __compiletime_object_size
 # define __compiletime_object_size(obj) -1
 #endif
+#ifndef __compiletime_warning
+# define __compiletime_warning(message)
+#endif
+
 /*
  * Prevent the compiler from merging or refetching accesses.  The compiler
  * is also forbidden from reordering successive instances of ACCESS_ONCE(),