From 7b68273f79e83911114fb07597f06cc3913c4227 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 27 Mar 2017 09:48:04 +0200 Subject: [PATCH] s390/uaccess: get_user() should zero on failure (again) commit d09c5373e8e4eaaa09233552cbf75dc4c4f21203 upstream. Commit fd2d2b191fe7 ("s390: get_user() should zero on failure") intended to fix s390's get_user() implementation which did not zero the target operand if the read from user space faulted. Unfortunately the patch has no effect: the corresponding inline assembly specifies that the operand is only written to ("=") and the previous value is discarded. Therefore the compiler is free to and actually does omit the zero initialization. To fix this simply change the contraint modifier to "+", so the compiler cannot omit the initialization anymore. Fixes: c9ca78415ac1 ("s390/uaccess: provide inline variants of get_user/put_user") Fixes: fd2d2b191fe7 ("s390: get_user() should zero on failure") Cc: Al Viro Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h index 52d7c8709279..a7ef70220126 100644 --- a/arch/s390/include/asm/uaccess.h +++ b/arch/s390/include/asm/uaccess.h @@ -144,7 +144,7 @@ unsigned long __must_check __copy_to_user(void __user *to, const void *from, " jg 2b\n" \ ".popsection\n" \ EX_TABLE(0b,3b) EX_TABLE(1b,3b) \ - : "=d" (__rc), "=Q" (*(to)) \ + : "=d" (__rc), "+Q" (*(to)) \ : "d" (size), "Q" (*(from)), \ "d" (__reg0), "K" (-EFAULT) \ : "cc"); \