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Commit d6cbf35d authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
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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: default avatarIvan Bulatovic <combuster@archlinux.us>
Reported-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarTejun 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;

	}