| From d09c5373e8e4eaaa09233552cbf75dc4c4f21203 Mon Sep 17 00:00:00 2001 |
| From: Heiko Carstens <heiko.carstens@de.ibm.com> |
| Date: Mon, 27 Mar 2017 09:48:04 +0200 |
| Subject: s390/uaccess: get_user() should zero on failure (again) |
| |
| From: Heiko Carstens <heiko.carstens@de.ibm.com> |
| |
| 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 <viro@zeniv.linux.org.uk> |
| Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> |
| Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/s390/include/asm/uaccess.h | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/arch/s390/include/asm/uaccess.h |
| +++ b/arch/s390/include/asm/uaccess.h |
| @@ -150,7 +150,7 @@ unsigned long __must_check __copy_to_use |
| " 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"); \ |
