[PATCH] inotify: actually check for invalid bits in sys_inotify_add_watch()

[Dave Hansen <dave@sr71.net>]

From: Dave Hansen <dave.hansen@linux.intel.com>

The comment here says that it is checking for invalid bits.  But,
the mask is *actually* checking to ensure that _any_ valid bit
is set, which is quite different.

Add the actual check which was intended.  Retain the existing
check because it actually does something useful: ensure that some
inotify bits are being added to the watch.  Plus, this is
existing behavior which would be nice to preserve.

I did a quick sniff test that inotify functions and that my
'inotify-tools' package passes 'make check'.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: John McCutchan <john@johnmccutchan.com> (maintainer:INOTIFY)
Cc: Robert Love <rlove@rlove.org> (maintainer:INOTIFY)
Cc: Eric Paris <eparis@parisplace.org> (maintainer:INOTIFY)
Cc: linux-kernel@vger.kernel.org (open list)
Cc: stable@vger.kernel.org
---

 b/fs/notify/inotify/inotify_user.c |    3 +++
 1 file changed, 3 insertions(+)

diff -puN fs/notify/inotify/inotify_user.c~inotify-EINVAL-on-invalid-bit fs/notify/inotify/inotify_user.c
--- a/fs/notify/inotify/inotify_user.c~inotify-EINVAL-on-invalid-bit	2015-06-26 13:33:30.277219285 -0700
+++ b/fs/notify/inotify/inotify_user.c	2015-06-26 13:35:19.026122033 -0700
@@ -707,6 +707,9 @@ SYSCALL_DEFINE3(inotify_add_watch, int,
 	unsigned flags = 0;
 
 	/* don't allow invalid bits: we don't want flags set */
+	if (unlikely(mask & ~ALL_INOTIFY_BITS))
+		return -EINVAL;
+	/* require at least one valid bit set in the mask */
 	if (unlikely(!(mask & ALL_INOTIFY_BITS)))
 		return -EINVAL;
 
_