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>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2a99262..38b1365 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2699,13 +2699,14 @@
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;
}