From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx183.postini.com [74.125.245.183]) by kanga.kvack.org (Postfix) with SMTP id 868516B0032 for ; Sun, 1 Sep 2013 15:59:17 -0400 (EDT) From: Richard Hansen Subject: [PATCH] mm: msync: require either MS_ASYNC or MS_SYNC Date: Sun, 1 Sep 2013 15:58:57 -0400 Message-Id: <1378065537-7222-1-git-send-email-rhansen@bbn.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: linux-api@vger.kernel.org, Richard Hansen For the flags parameter, POSIX says "Either MS_ASYNC or MS_SYNC shall be specified, but not both." [1] There was already a test for the "both" condition. Add a test to ensure that the caller specified one of the flags; fail with EINVAL if neither are specified. Without this change, specifying neither is the same as specifying flags=MS_ASYNC because nothing in msync() is conditioned on the MS_ASYNC flag. This has not always been true, and there's no good reason to believe that this behavior would have persisted indefinitely. The msync(2) man page (as currently written in man-pages.git) is silent on the behavior if both flags are unset, so this change should not break an application written by somone who carefully reads the Linux man pages or the POSIX spec. [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/msync.html Signed-off-by: Richard Hansen Reported-by: Greg Troxel Reviewed-by: Greg Troxel --- mm/msync.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/msync.c b/mm/msync.c index 632df45..472ad3e 100644 --- a/mm/msync.c +++ b/mm/msync.c @@ -42,6 +42,8 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) goto out; if ((flags & MS_ASYNC) && (flags & MS_SYNC)) goto out; + if (!(flags & (MS_ASYNC | MS_SYNC))) + goto out; error = -ENOMEM; len = (len + ~PAGE_MASK) & PAGE_MASK; end = start + len; -- 1.8.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org