x86/uaccess: instrument copy_from_user_nmi()

Make sure usercopy hooks from linux/instrumented.h are invoked for
copy_from_user_nmi().  This fixes KMSAN false positives reported when
dumping opcodes for a stack trace.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alexander Potapenko <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: ramosian-glider

arch/x86/lib/usercopy.c

@@ -6,6 +6,7 @@
 
 #include <linux/uaccess.h>
 #include <linux/export.h>
+#include <linux/instrumented.h>
 
 #include <asm/tlbflush.h>
 
@@ -44,7 +45,9 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
 	 * called from other contexts.
 	 */
 	pagefault_disable();
+	instrument_copy_from_user_before(to, from, n);
 	ret = raw_copy_from_user(to, from, n);
+	instrument_copy_from_user_after(to, from, n, ret);
 	pagefault_enable();
 
 	return ret;