Commit 6160968c authored Aug 06, 2013 by Oleg Nesterov Committed by Linus Torvalds Aug 06, 2013

userns: unshare_userns(&cred) should not populate cred on failure



unshare_userns(new_cred) does *new_cred = prepare_creds() before
create_user_ns() which can fail. However, the caller expects that
it doesn't need to take care of new_cred if unshare_userns() fails.

We could change the single caller, sys_unshare(), but I think it
would be more clean to avoid the side effects on failure, so with
this patch unshare_userns() does put_cred() itself and initializes
*new_cred only if create_user_ns() succeeeds.

Cc: stable@vger.kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent c095ba72

kernel/user_namespace.c

+9 −4

Original line number	Original line	Diff line number	Diff line
	@@ -105,16 +105,21 @@ int create_user_ns(struct cred *new)
	int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)		int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
	{		{
	struct cred *cred;		struct cred *cred;
			int err = -ENOMEM;

	if (!(unshare_flags & CLONE_NEWUSER))		if (!(unshare_flags & CLONE_NEWUSER))
	return 0;		return 0;

	cred = prepare_creds();		cred = prepare_creds();
	if (!cred)		if (cred) {
	return -ENOMEM;		err = create_user_ns(cred);
			if (err)
			put_cred(cred);
			else
	*new_cred = cred;		*new_cred = cred;
	return create_user_ns(cred);		}

			return err;
	}		}

	void free_user_ns(struct user_namespace *ns)		void free_user_ns(struct user_namespace *ns)