Commit d6cbf35d authored May 14, 2013 by Li Zefan Committed by Tejun Heo May 14, 2013

cgroup: initialize xattr before calling d_instantiate()



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.

Cc: <stable@vger.kernel.org> # 3.8.x
Reported-by: Ivan Bulatovic <combuster@archlinux.us>
Reported-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

parent f722406f

kernel/cgroup.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -2699,13 +2699,14 @@ static int cgroup_add_file(struct cgroup cgrp, struct cgroup_subsys subsys,
		goto out;
		}

		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);

		mode = cgroup_file_mode(cft);
		error = cgroup_create_file(dentry, mode \| S_IFREG, cgrp->root->sb);
		if (!error) {
		list_add_tail(&cfe->node, &parent->files);
		cfe = NULL;
		}

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