From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752172AbaILOm2 (ORCPT ); Fri, 12 Sep 2014 10:42:28 -0400 Received: from mail-oi0-f42.google.com ([209.85.218.42]:35700 "EHLO mail-oi0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751931AbaILOmT (ORCPT ); Fri, 12 Sep 2014 10:42:19 -0400 From: Seth Forshee To: Miklos Szeredi , Alexander Viro , "Eric W. Biederman" Cc: Serge Hallyn , fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Seth Forshee Subject: [PATCH v3 1/4] vfs: Check for invalid i_uid in may_follow_link() Date: Fri, 12 Sep 2014 09:41:42 -0500 Message-Id: <1410532905-114262-2-git-send-email-seth.forshee@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1410532905-114262-1-git-send-email-seth.forshee@canonical.com> References: <1410532905-114262-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Filesystem uids which don't map into a user namespace may result in inode->i_uid being INVALID_UID. A symlink and its parent could have different owners in the filesystem can both get mapped to INVALID_UID, which may result in following a symlink when this would not have otherwise been permitted. Prevent this by adding a check that the uid is valid before the comparison. Signed-off-by: Seth Forshee Acked-by: Serge E. Hallyn --- fs/namei.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index a996bb48dfab..193da09e903e 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -741,7 +741,7 @@ static inline int may_follow_link(struct path *link, struct nameidata *nd) return 0; /* Allowed if parent directory and link owner match. */ - if (uid_eq(parent->i_uid, inode->i_uid)) + if (uid_valid(inode->i_uid) && uid_eq(parent->i_uid, inode->i_uid)) return 0; audit_log_link_denied("follow_link", link); -- 1.9.1