Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752084Ab0GNGSr (ORCPT ); Wed, 14 Jul 2010 02:18:47 -0400 Received: from smtp.outflux.net ([198.145.64.163]:53564 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750959Ab0GNGSq (ORCPT ); Wed, 14 Jul 2010 02:18:46 -0400 Date: Tue, 13 Jul 2010 23:18:45 -0700 From: Kees Cook To: linux-security-module@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH v2] Yama: verify inode is symlink to avoid bind mounts Message-ID: <20100714061845.GW6104@outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Organization: Canonical X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1316 Lines: 44 The inode_follow_link LSM hook is called in bind mount situations as well as for symlink situations, so we must explicitly check for the inode being a symlink to not reject bind mounts in 1777 directories, which seems to be a common NFSv4 configuration. Signed-off-by: Kees Cook --- v2: - actually set inode in time to use it. *face palm* --- security/yama/yama_lsm.c | 6 +++++- 1 files changed, 5 insertions(+), 1 deletions(-) diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index 3b76386..51c6a3a 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -116,9 +116,13 @@ static int yama_inode_follow_link(struct dentry *dentry, if (!protected_sticky_symlinks) return 0; + /* if inode isn't a symlink, don't try to evaluate blocking it */ + inode = dentry->d_inode; + if (!S_ISLNK(inode->i_mode)) + return 0; + /* owner and follower match? */ cred = current_cred(); - inode = dentry->d_inode; if (cred->fsuid == inode->i_uid) return 0; -- 1.7.1 -- Kees Cook Ubuntu Security Team -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/