linux-kernel - [PATCH mmotm/next] fanotify: fix corruption preventing startup

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Message-ID: <alpine.LSU.2.11.1401112245290.4960@eggly.anvils>
Date:	Sat, 11 Jan 2014 22:54:15 -0800 (PST)
From:	Hugh Dickins <hughd@...gle.com>
To:	Jan Kara <jack@...e.cz>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH mmotm/next] fanotify: fix corruption preventing startup

Two of my machines couldn't boot mmotm with fanotify enabled:
0x40000020 was being or'ed into a group's notification_waitq next
pointer, with sad results.  It comes from an over-simplification in
fanotify_merge(): test_event isn't NULL when the loop finds no merge.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
Fixes fsnotify-do-not-share-events-between-notification-groups.patch

 fs/notify/fanotify/fanotify.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- mmotm/fs/notify/fanotify/fanotify.c	2014-01-10 18:25:01.700448941 -0800
+++ linux/fs/notify/fanotify/fanotify.c	2014-01-11 22:15:31.580961010 -0800
@@ -37,16 +37,19 @@ static bool should_merge(struct fsnotify
 static struct fsnotify_event *fanotify_merge(struct list_head *list,
 					     struct fsnotify_event *event)
 {
-	struct fsnotify_event *test_event = NULL;
+	struct fsnotify_event *test_event;
+	bool do_merge = false;
 
 	pr_debug("%s: list=%p event=%p\n", __func__, list, event);
 
 	list_for_each_entry_reverse(test_event, list, list) {
-		if (should_merge(test_event, event))
+		if (should_merge(test_event, event)) {
+			do_merge = true;
 			break;
+		}
 	}
 
-	if (!test_event)
+	if (!do_merge)
 		return NULL;
 
 	test_event->mask |= event->mask;
--
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