On 2013/5/11 6:02, Casey Schaufler wrote:
>
> In kernel/cgroup.c in cgroup_add_file() we have:
>
>
> dentry = lookup_one_len(name, dir, strlen(name));
> if (IS_ERR(dentry)) {
> error = PTR_ERR(dentry);
> 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);
> list_add_tail(&cfe->node, &parent->files);
> cfe = NULL;
> }
> dput(dentry);
>
> 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, although
> no one seems to be using that option. Since the dentry
> has not been initialized panics in __d_xattr ensue. See
> bugzilla 57791.
>
cgroup_add_file() should initialize xattrs before calling d_instantiate(),
just like cgroup_create() does.
I'll prepare a patch to fix it. Thanks for the report!
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