linux-kernel - [ 080/127] cgroup: initialize xattr before calling d

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Date:	Wed,  5 Jun 2013 14:34:07 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Ivan Bulatovic <combuster@...hlinux.us>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Li Zefan <lizefan@...wei.com>, Tejun Heo <tj@...nel.org>
Subject: [ 080/127] cgroup: initialize xattr before calling d_instantiate()

3.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Li Zefan <lizefan@...wei.com>

commit d6cbf35dac8a3dadb9103379820c96d7c85df3d9 upstream.

cgroup_create_file() calls d_instantiate(), which may decide to look
at the xattrs on the file. Smack always does this and SELinux can be
configured to do so.

But cgroup_add_file() didn't initialize xattrs before calling
cgroup_create_file(), which finally leads to dereferencing NULL
dentry->d_fsdata.

This bug has been there since cgroup xattr was introduced.

Reported-by: Ivan Bulatovic <combuster@...hlinux.us>
Reported-by: Casey Schaufler <casey@...aufler-ca.com>
Signed-off-by: Li Zefan <lizefan@...wei.com>
Signed-off-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/cgroup.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2747,13 +2747,14 @@ static int cgroup_add_file(struct cgroup
 		goto out;
 	}
 
+	cfe->type = (void *)cft;
+	cfe->dentry = dentry;
+	dentry->d_fsdata = cfe;
+	simple_xattrs_init(&cfe->xattrs);
+
 	mode = cgroup_file_mode(cft);
 	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
 	if (!error) {
-		cfe->type = (void *)cft;
-		cfe->dentry = dentry;
-		dentry->d_fsdata = cfe;
-		simple_xattrs_init(&cfe->xattrs);
 		list_add_tail(&cfe->node, &parent->files);
 		cfe = NULL;
 	}


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