linux-kernel - [PATCH 4/4] ext4: use file

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Message-Id: <1458205323-25685-4-git-send-email-miklos@szeredi.hu>
Date:	Thu, 17 Mar 2016 10:02:03 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:	dhowells@...hat.com, viro@...iv.linux.org.uk,
	Daniel Axtens <dja@...ens.net>, Theodore Ts'o <tytso@....edu>,
	<stable@...r.kernel.org>
Subject: [PATCH 4/4] ext4: use file_dentry()

From: Miklos Szeredi <mszeredi@...hat.com>

EXT4 may be used as lower layer of overlayfs and accessing f_path.dentry
can lead to a crash.

Fix by replacing direct access of file->f_path.dentry with the
file_dentry() accessor, which will always return a native object.

Reported-by: Daniel Axtens <dja@...ens.net>
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Fixes: ff978b09f973 ("ext4 crypto: move context consistency check to ext4_file_open()")
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Cc: Theodore Ts'o <tytso@....edu>
Cc: David Howells <dhowells@...hat.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: <stable@...r.kernel.org> # v4.5
---
 fs/ext4/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index feb9ffc6f20d..38847f38b34a 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -380,7 +380,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
 			return -ENOKEY;
 	}
 
-	dir = dget_parent(filp->f_path.dentry);
+	dir = dget_parent(file_dentry(filp));
 	if (ext4_encrypted_inode(d_inode(dir)) &&
 	    !ext4_is_child_context_consistent_with_parent(d_inode(dir), inode)) {
 		ext4_warning(inode->i_sb,
-- 
2.1.4