From d9d9e275a9a31fbd6f085bbd809d15753137d0a4 Mon Sep 17 00:00:00 2001
From: Kris Van Hees <kris.van.hees@oracle.com>
Date: Tue, 12 Dec 2017 13:19:21 -0500
Subject: [PATCH] dtrace: do not use copy_from_user when accessing kernel stack

The implementation of sdt_getarg() for x86_64 uses a copy_from_user
variant while reading from kernel stack which is obviously wrong.
This commit corrects that.

Orabug: 25949088
Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Tomas Jedlicka <tomas.jedlicka@oracle.com>
---
 arch/x86/dtrace/sdt_x86_64.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/dtrace/sdt_x86_64.c b/arch/x86/dtrace/sdt_x86_64.c
index edfc30f29574..40f18d488e34 100644
--- a/arch/x86/dtrace/sdt_x86_64.c
+++ b/arch/x86/dtrace/sdt_x86_64.c
@@ -17,7 +17,6 @@
 
 #include <linux/sdt.h>
 #include <linux/slab.h>
-#include <linux/uaccess.h>
 #include <linux/vmalloc.h>
 #include <asm/dtrace_util.h>
 
@@ -105,8 +104,7 @@ uint64_t sdt_getarg(void *arg, dtrace_id_t id, void *parg, int argno,
 
 	st = (uint64_t *)regs->sp;
 	DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
-	__copy_from_user_inatomic_nocache(&val, (void *)&st[argno - 6],
-					  sizeof(st[0]));
+	val = st[argno - 6];
 	DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
 
 	return val;
-- 
2.50.1