linux-kernel - [PATCH 1/2] fsnotify: fix NULL dereference in send_to

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Date:	Sun, 29 Aug 2010 00:55:41 +0530
From:	Csaba Henk <csaba@...ster.com>
To:	linux-kernel@...r.kernel.org
Cc:	Eric Paris <eparis@...hat.com>, Csaba Henk <csaba@...ster.com>
Subject: [PATCH 1/2] fsnotify: fix NULL dereference in send_to_group()

If fanotify is triggered via a vfsmount mark (so that there is
no inode mark, group in send_to_group() is set from a structure
member where the struct pointer is NULL.

This can be tested with the fanotify utility available from
http://people.redhat.com/eparis/fanotify/:

 # fanotify -m / & touch /x

Signed-off-by: Csaba Henk <csaba@...ster.com>
---
 fs/notify/fsnotify.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 3970392..6657315 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -148,13 +148,21 @@ static int send_to_group(struct inode *to_tell, struct vfsmount *mnt,
 			 const unsigned char *file_name,
 			 struct fsnotify_event **event)
 {
-	struct fsnotify_group *group = inode_mark->group;
+	struct fsnotify_group *group;
 	__u32 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 	__u32 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 
-	pr_debug("%s: group=%p to_tell=%p mnt=%p mark=%p mask=%x data=%p"
-		 " data_is=%d cookie=%d event=%p\n", __func__, group, to_tell,
-		 mnt, inode_mark, mask, data, data_is, cookie, *event);
+	if (inode_mark)
+		group = inode_mark->group;
+	else if (vfsmount_mark)
+		group = vfsmount_mark->group;
+	else
+		BUG();
+
+	pr_debug("%s: group=%p to_tell=%p mnt=%p inode_mark=%p vfsmount_mark=%p"
+		 " mask=%x data=%p data_is=%d cookie=%d event=%p\n",
+		 __func__, group, to_tell, mnt, inode_mark, vfsmount_mark, mask,
+		 data, data_is, cookie, *event);
 
 	/* clear ignored on inode modification */
 	if (mask & FS_MODIFY) {
-- 
1.7.2.2

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