From 3587b1b097d70c2eb9fee95ea7995d13c05f66e5 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@ZenIV.linux.org.uk>
Date: Sun, 18 Nov 2012 19:19:00 +0000
Subject: fanotify: fix FAN_Q_OVERFLOW case of fanotify_read()

If the FAN_Q_OVERFLOW bit set in event->mask, the fanotify event
metadata will not contain a valid file descriptor, but
copy_event_to_user() didn't check for that, and unconditionally does a
fd_install() on the file descriptor.

Which in turn will cause a BUG_ON() in __fd_install().

Introduced by commit 352e3b249284 ("fanotify: sanitize failure exits in
copy_event_to_user()")

Mea culpa - missed that path ;-/

Reported-by: Alex Shi <lkml.alex@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 fs/notify/fanotify/fanotify_user.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'fs/notify/fanotify')

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 721d692fa8d4..6fcaeb8c902e 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -258,7 +258,8 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 	if (ret)
 		goto out_close_fd;
 
-	fd_install(fd, f);
+	if (fd != FAN_NOFD)
+		fd_install(fd, f);
 	return fanotify_event_metadata.event_len;
 
 out_close_fd:
-- 
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